/[pcre]/code/trunk/doc/pcre.txt

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-revision 289 by ph10,
Sun Dec 23 12:17:20 2007 UTC
+revision 469 by ph10,
Mon Oct 19 14:38:48 2009 UTC
 Line 2
  This file contains a concatenation of the PCRE man pages, converted to plain
  text format for ease of searching with a text editor, or for use on systems
  that do not have a man page processor. The small individual files that give
- synopses of each function in the library have not been included. There are
+ synopses of each function in the library have not been included. Neither has
- separate text files for the pcregrep and pcretest commands.
+ the pcredemo program. There are separate text files for the pcregrep and
+ pcretest commands.
  -----------------------------------------------------------------------------
-Line 18 
 INTRODUCTION
+Line 19 
 INTRODUCTION
         The  PCRE  library is a set of functions that implement regular expres-
         sion pattern matching using the same syntax and semantics as Perl, with
-        just  a  few differences. (Certain features that appeared in Python and
+        just  a few differences. Some features that appeared in Python and PCRE
-        PCRE before they appeared in Perl are also available using  the  Python
+        before they appeared in Perl are also available using the  Python  syn-
-        syntax.)
+        tax,  there  is  some  support for one or two .NET and Oniguruma syntax
+        items, and there is an option for requesting some  minor  changes  that
-        The  current  implementation of PCRE (release 7.x) corresponds approxi-
+        give better JavaScript compatibility.
-        mately with Perl 5.10, including support for UTF-8 encoded strings  and
-        Unicode general category properties. However, UTF-8 and Unicode support
+        The  current implementation of PCRE corresponds approximately with Perl
-        has to be explicitly enabled; it is not the default. The Unicode tables
+.10, including support for UTF-8 encoded strings and  Unicode  general
-        correspond to Unicode release 5.0.0.
+        category  properties.  However,  UTF-8  and  Unicode  support has to be
+        explicitly enabled; it is not the default. The  Unicode  tables  corre-
+        spond to Unicode release 5.1.
         In  addition to the Perl-compatible matching function, PCRE contains an
-        alternative matching function that matches the same  compiled  patterns
+        alternative function that matches the same compiled patterns in a  dif-
-        in  a different way. In certain circumstances, the alternative function
+        ferent way. In certain circumstances, the alternative function has some
-        has some advantages. For a discussion of the two  matching  algorithms,
+        advantages.  For a discussion of the two matching algorithms,  see  the
-        see the pcrematching page.
+        pcrematching page.
         PCRE  is  written  in C and released as a C library. A number of people
         have written wrappers and interfaces of various kinds.  In  particular,
-Line 52 
 INTRODUCTION
+Line 55 
 INTRODUCTION
         library is built. The pcre_config() function makes it  possible  for  a
         client  to  discover  which  features are available. The features them-
         selves are described in the pcrebuild page. Documentation about  build-
-        ing  PCRE for various operating systems can be found in the README file
+        ing  PCRE  for various operating systems can be found in the README and
-        in the source distribution.
+        NON-UNIX-USE files in the source distribution.
         The library contains a number of undocumented  internal  functions  and
         data  tables  that  are  used by more than one of the exported external
-Line 69 
 USER DOCUMENTATION
+Line 72 
 USER DOCUMENTATION
         The user documentation for PCRE comprises a number  of  different  sec-
         tions.  In the "man" format, each of these is a separate "man page". In
         the HTML format, each is a separate page, linked from the  index  page.
-        In  the  plain text format, all the sections are concatenated, for ease
+        In  the  plain  text format, all the sections, except the pcredemo sec-
-        of searching. The sections are as follows:
+        tion, are concatenated, for ease of searching. The sections are as fol-
+        lows:
           pcre              this document
           pcre-config       show PCRE installation configuration information
-Line 79 
 USER DOCUMENTATION
+Line 83 
 USER DOCUMENTATION
           pcrecallout       details of the callout feature
           pcrecompat        discussion of Perl compatibility
           pcrecpp           details of the C++ wrapper
+          pcredemo          a demonstration C program that uses PCRE
           pcregrep          description of the pcregrep command
           pcrematching      discussion of the two matching algorithms
           pcrepartial       details of the partial matching facility
           pcrepattern       syntax and semantics of supported
                               regular expressions
-          pcresyntax        quick syntax reference
           pcreperform       discussion of performance issues
           pcreposix         the POSIX-compatible C API
           pcreprecompile    details of saving and re-using precompiled patterns
-          pcresample        discussion of the sample program
+          pcresample        discussion of the pcredemo program
           pcrestack         discussion of stack usage
+          pcresyntax        quick syntax reference
           pcretest          description of the pcretest testing command
         In  addition,  in the "man" and HTML formats, there is a short page for
-Line 134 
 UTF-8 AND UNICODE PROPERTY SUPPORT
+Line 139 
 UTF-8 AND UNICODE PROPERTY SUPPORT
         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
         support in the code, and, in addition,  you  must  call  pcre_compile()
-        with  the PCRE_UTF8 option flag. When you do this, both the pattern and
+        with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
-        any subject strings that are matched against it are  treated  as  UTF-8
+        sequence (*UTF8). When either of these is the case,  both  the  pattern
-        strings instead of just strings of bytes.
+        and  any  subject  strings  that  are matched against it are treated as
+        UTF-8 strings instead of strings of 1-byte characters.
-        If  you compile PCRE with UTF-8 support, but do not use it at run time,
+        If you compile PCRE with UTF-8 support, but do not use it at run  time,
-        the library will be a bit bigger, but the additional run time  overhead
+        the  library will be a bit bigger, but the additional run time overhead
         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
         very big.
         If PCRE is built with Unicode character property support (which implies
-        UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
+        UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
         ported.  The available properties that can be tested are limited to the
-        general  category  properties such as Lu for an upper case letter or Nd
+        general category properties such as Lu for an upper case letter  or  Nd
-        for a decimal number, the Unicode script names such as Arabic  or  Han,
+        for  a  decimal number, the Unicode script names such as Arabic or Han,
-        and  the  derived  properties  Any  and L&. A full list is given in the
+        and the derived properties Any and L&. A full  list  is  given  in  the
         pcrepattern documentation. Only the short names for properties are sup-
-        ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
+        ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
-        ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
+        ter},  is  not  supported.   Furthermore,  in Perl, many properties may
-        optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
+        optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
         does not support this.
     Validity of UTF-8 strings
-        When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
+        When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
         subjects are (by default) checked for validity on entry to the relevant
-        functions. From release 7.3 of PCRE, the check is according  the  rules
+        functions.  From  release 7.3 of PCRE, the check is according the rules
-        of  RFC  3629, which are themselves derived from the Unicode specifica-
+        of RFC 3629, which are themselves derived from the  Unicode  specifica-
-        tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
+        tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
-        allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
+        allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
         to U+DFFF.
-        The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
+        The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
-        which the Unicode Standard says this: "The Low Surrogate Area does  not
+        which  the Unicode Standard says this: "The Low Surrogate Area does not
-        contain  any  character  assignments,  consequently  no  character code
+        contain any  character  assignments,  consequently  no  character  code
         charts or namelists are provided for this area. Surrogates are reserved
-        for  use  with  UTF-16 and then must be used in pairs." The code points
+        for use with UTF-16 and then must be used in pairs."  The  code  points
-        that are encoded by UTF-16 pairs  are  available  as  independent  code
+        that  are  encoded  by  UTF-16  pairs are available as independent code
-        points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
+        points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
-        If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
+        If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
         that your strings are valid, and therefore want to skip these checks in
         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
-        compile time or at run time, PCRE assumes that the pattern  or  subject
+        compile  time  or at run time, PCRE assumes that the pattern or subject
-        it  is  given  (respectively)  contains only valid UTF-8 codes. In this
+        it is given (respectively) contains only valid  UTF-8  codes.  In  this
         case, it does not diagnose an invalid UTF-8 string.
-        If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
+        If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
-        what  happens  depends on why the string is invalid. If the string con-
+        what happens depends on why the string is invalid. If the  string  con-
         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
-        string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
+        string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
         apart from the initial validity test, PCRE (when in UTF-8 mode) handles
-        strings  according  to  the more liberal rules of RFC 2279. However, if
+        strings according to the more liberal rules of RFC  2279.  However,  if
-        the string does not even conform to RFC 2279, the result is  undefined.
+        the  string does not even conform to RFC 2279, the result is undefined.
         Your program may crash.
-        If  you  want  to  process  strings  of  values  in the full range 0 to
+        If you want to process strings  of  values  in  the  full  range  0  to
-x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
+x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
         set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
         this situation, you will have to apply your own validity check.
     General comments about UTF-8 mode
-. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
+.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
         two-byte UTF-8 character if the value is greater than 127.
-.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8
+. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
         characters for values greater than \177.
-. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
+.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
         vidual bytes, for example: \x{100}{3}.
-.  The dot metacharacter matches one UTF-8 character instead of a sin-
+. The dot metacharacter matches one UTF-8 character instead of a  sin-
         gle byte.
-. The escape sequence \C can be used to match a single byte  in  UTF-8
+.  The  escape sequence \C can be used to match a single byte in UTF-8
-        mode,  but  its  use can lead to some strange effects. This facility is
+        mode, but its use can lead to some strange effects.  This  facility  is
         not available in the alternative matching function, pcre_dfa_exec().
-. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
+.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
-        test  characters of any code value, but the characters that PCRE recog-
+        test characters of any code value, but the characters that PCRE  recog-
-        nizes as digits, spaces, or word characters  remain  the  same  set  as
+        nizes  as  digits,  spaces,  or  word characters remain the same set as
         before, all with values less than 256. This remains true even when PCRE
-        includes Unicode property support, because to do otherwise  would  slow
+        includes  Unicode  property support, because to do otherwise would slow
-        down  PCRE in many common cases. If you really want to test for a wider
+        down PCRE in many common cases. If you really want to test for a  wider
-        sense of, say, "digit", you must use Unicode  property  tests  such  as
+        sense  of,  say,  "digit",  you must use Unicode property tests such as
-        \p{Nd}.
+        \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
+        terms of \w and \W.
 .  Similarly,  characters that match the POSIX named character classes
         are all low-valued characters.
-Line 256 
 AUTHOR
+Line 263 
 AUTHOR
  REVISION
-        Last updated: 09 August 2007
+        Last updated: 28 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 275 
 PCRE BUILD-TIME OPTIONS
+Line 282 
 PCRE BUILD-TIME OPTIONS
         script,  where the optional features are selected or deselected by pro-
         viding options to configure before running the make  command.  However,
         the  same  options  can be selected in both Unix-like and non-Unix-like
-        environments using the GUI facility of  CMakeSetup  if  you  are  using
+        environments using the GUI facility of cmake-gui if you are using CMake
-        CMake instead of configure to build PCRE.
+        instead of configure to build PCRE.
+        There  is  a  lot more information about building PCRE in non-Unix-like
+        environments in the file called NON_UNIX_USE, which is part of the PCRE
+        distribution.  You  should consult this file as well as the README file
+        if you are building in a non-Unix-like environment.
         The complete list of options for configure (which includes the standard
-        ones such as the  selection  of  the  installation  directory)  can  be
+        ones  such  as  the  selection  of  the  installation directory) can be
         obtained by running
           ./configure --help
-        The  following  sections  include  descriptions  of options whose names
+        The following sections include  descriptions  of  options  whose  names
         begin with --enable or --disable. These settings specify changes to the
-        defaults  for  the configure command. Because of the way that configure
+        defaults for the configure command. Because of the way  that  configure
-        works, --enable and --disable always come in pairs, so  the  complemen-
+        works,  --enable  and --disable always come in pairs, so the complemen-
-        tary  option always exists as well, but as it specifies the default, it
+        tary option always exists as well, but as it specifies the default,  it
         is not described.
-Line 305 
 C++ SUPPORT
+Line 317 
 C++ SUPPORT
  UTF-8 SUPPORT
-        To build PCRE with support for UTF-8 character strings, add
+        To build PCRE with support for UTF-8 Unicode character strings, add
           --enable-utf8
-        to the configure command. Of itself, this  does  not  make  PCRE  treat
+        to  the  configure  command.  Of  itself, this does not make PCRE treat
-        strings  as UTF-8. As well as compiling PCRE with this option, you also
+        strings as UTF-8. As well as compiling PCRE with this option, you  also
-        have have to set the PCRE_UTF8 option when you call the  pcre_compile()
+        have  have to set the PCRE_UTF8 option when you call the pcre_compile()
-        function.
+        or pcre_compile2() functions.
+        If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
+        expects its input to be either ASCII or UTF-8 (depending on the runtime
+        option). It is not possible to support both EBCDIC and UTF-8  codes  in
+        the  same  version  of  the  library.  Consequently,  --enable-utf8 and
+        --enable-ebcdic are mutually exclusive.
  UNICODE CHARACTER PROPERTY SUPPORT
-        UTF-8  support allows PCRE to process character values greater than 255
+        UTF-8 support allows PCRE to process character values greater than  255
-        in the strings that it handles. On its own, however, it does  not  pro-
+        in  the  strings that it handles. On its own, however, it does not pro-
         vide any facilities for accessing the properties of such characters. If
-        you want to be able to use the pattern escapes \P, \p,  and  \X,  which
+        you  want  to  be able to use the pattern escapes \P, \p, and \X, which
         refer to Unicode character properties, you must add
           --enable-unicode-properties
-        to  the configure command. This implies UTF-8 support, even if you have
+        to the configure command. This implies UTF-8 support, even if you  have
         not explicitly requested it.
-        Including Unicode property support adds around 30K  of  tables  to  the
+        Including  Unicode  property  support  adds around 30K of tables to the
-        PCRE  library.  Only  the general category properties such as Lu and Nd
+        PCRE library. Only the general category properties such as  Lu  and  Nd
         are supported. Details are given in the pcrepattern documentation.
  CODE VALUE OF NEWLINE
-        By default, PCRE interprets character 10 (linefeed, LF)  as  indicating
+        By  default,  PCRE interprets the linefeed (LF) character as indicating
-        the  end  of  a line. This is the normal newline character on Unix-like
+        the end of a line. This is the normal newline  character  on  Unix-like
-        systems. You can compile PCRE to use character 13 (carriage return, CR)
+        systems.  You  can compile PCRE to use carriage return (CR) instead, by
-        instead, by adding
+        adding
           --enable-newline-is-cr
-        to  the  configure  command.  There  is  also  a --enable-newline-is-lf
+        to the  configure  command.  There  is  also  a  --enable-newline-is-lf
         option, which explicitly specifies linefeed as the newline character.
         Alternatively, you can specify that line endings are to be indicated by
-Line 354 
 CODE VALUE OF NEWLINE
+Line 372 
 CODE VALUE OF NEWLINE
           --enable-newline-is-anycrlf
-        which  causes  PCRE  to recognize any of the three sequences CR, LF, or
+        which causes PCRE to recognize any of the three sequences  CR,  LF,  or
         CRLF as indicating a line ending. Finally, a fifth option, specified by
           --enable-newline-is-any
-Line 414 
 HANDLING VERY LARGE PATTERNS
+Line 432 
 HANDLING VERY LARGE PATTERNS
         nation metacharacter). By default, two-byte values are used  for  these
         offsets,  leading  to  a  maximum size for a compiled pattern of around
 K. This is sufficient to handle all but the most  gigantic  patterns.
-        Nevertheless,  some  people do want to process enormous patterns, so it
+        Nevertheless,  some  people do want to process truyl enormous patterns,
-        is possible to compile PCRE to use three-byte or four-byte  offsets  by
+        so it is possible to compile PCRE to use three-byte or  four-byte  off-
-        adding a setting such as
+        sets by adding a setting such as
           --with-link-size=3
-Line 443 
 AVOIDING EXCESSIVE STACK USAGE
+Line 461 
 AVOIDING EXCESSIVE STACK USAGE
         to the configure command. With this configuration, PCRE  will  use  the
         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
         ment functions. By default these point to malloc() and free(), but  you
-        can replace the pointers so that your own functions are used.
+        can replace the pointers so that your own functions are used instead.
         Separate  functions  are  provided  rather  than  using pcre_malloc and
         pcre_free because the  usage  is  very  predictable:  the  block  sizes
-Line 451 
 AVOIDING EXCESSIVE STACK USAGE
+Line 469 
 AVOIDING EXCESSIVE STACK USAGE
         reverse order. A calling program might be able to  implement  optimized
         functions  that  perform  better  than  malloc()  and free(). PCRE runs
         noticeably more slowly when built in this way. This option affects only
-        the   pcre_exec()   function;   it   is   not   relevant  for  the  the
+        the pcre_exec() function; it is not relevant for pcre_dfa_exec().
-        pcre_dfa_exec() function.
  LIMITING PCRE RESOURCE USAGE
-        Internally, PCRE has a function called match(), which it calls  repeat-
+        Internally,  PCRE has a function called match(), which it calls repeat-
-        edly   (sometimes   recursively)  when  matching  a  pattern  with  the
+        edly  (sometimes  recursively)  when  matching  a  pattern   with   the
-        pcre_exec() function. By controlling the maximum number of  times  this
+        pcre_exec()  function.  By controlling the maximum number of times this
-        function  may be called during a single matching operation, a limit can
+        function may be called during a single matching operation, a limit  can
-        be placed on the resources used by a single call  to  pcre_exec().  The
+        be  placed  on  the resources used by a single call to pcre_exec(). The
-        limit  can be changed at run time, as described in the pcreapi documen-
+        limit can be changed at run time, as described in the pcreapi  documen-
-        tation. The default is 10 million, but this can be changed by adding  a
+        tation.  The default is 10 million, but this can be changed by adding a
         setting such as
           --with-match-limit=500000
-        to   the   configure  command.  This  setting  has  no  effect  on  the
+        to  the  configure  command.  This  setting  has  no  effect   on   the
         pcre_dfa_exec() matching function.
-        In some environments it is desirable to limit the  depth  of  recursive
+        In  some  environments  it is desirable to limit the depth of recursive
         calls of match() more strictly than the total number of calls, in order
-        to restrict the maximum amount of stack (or heap,  if  --disable-stack-
+        to  restrict  the maximum amount of stack (or heap, if --disable-stack-
         for-recursion is specified) that is used. A second limit controls this;
-        it defaults to the value that  is  set  for  --with-match-limit,  which
+        it  defaults  to  the  value  that is set for --with-match-limit, which
-        imposes  no  additional constraints. However, you can set a lower limit
+        imposes no additional constraints. However, you can set a  lower  limit
         by adding, for example,
           --with-match-limit-recursion=10000
-        to the configure command. This value can  also  be  overridden  at  run
+        to  the  configure  command.  This  value can also be overridden at run
         time.
  CREATING CHARACTER TABLES AT BUILD TIME
-        PCRE  uses fixed tables for processing characters whose code values are
+        PCRE uses fixed tables for processing characters whose code values  are
-        less than 256. By default, PCRE is built with a set of tables that  are
+        less  than 256. By default, PCRE is built with a set of tables that are
-        distributed  in  the  file pcre_chartables.c.dist. These tables are for
+        distributed in the file pcre_chartables.c.dist. These  tables  are  for
         ASCII codes only. If you add
           --enable-rebuild-chartables
-        to the configure command, the distributed tables are  no  longer  used.
+        to  the  configure  command, the distributed tables are no longer used.
-        Instead,  a  program  called dftables is compiled and run. This outputs
+        Instead, a program called dftables is compiled and  run.  This  outputs
         the source for new set of tables, created in the default locale of your
         C runtime system. (This method of replacing the tables does not work if
-        you are cross compiling, because dftables is run on the local host.  If
+        you  are cross compiling, because dftables is run on the local host. If
-        you  need  to  create alternative tables when cross compiling, you will
+        you need to create alternative tables when cross  compiling,  you  will
         have to do so "by hand".)
  USING EBCDIC CODE
-        PCRE assumes by default that it will run in an  environment  where  the
+        PCRE  assumes  by  default that it will run in an environment where the
-        character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
+        character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
-        This is the case for most computer operating systems.  PCRE  can,  how-
+        This  is  the  case for most computer operating systems. PCRE can, how-
         ever, be compiled to run in an EBCDIC environment by adding
           --enable-ebcdic
         to the configure command. This setting implies --enable-rebuild-charta-
-        bles. You should only use it if you know that  you  are  in  an  EBCDIC
+        bles.  You  should  only  use  it if you know that you are in an EBCDIC
-        environment (for example, an IBM mainframe operating system).
+        environment (for example,  an  IBM  mainframe  operating  system).  The
+        --enable-ebcdic option is incompatible with --enable-utf8.
  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
-Line 540 
 PCRETEST OPTION FOR LIBREADLINE SUPPORT
+Line 558 
 PCRETEST OPTION FOR LIBREADLINE SUPPORT
         to  the  configure  command,  pcretest  is  linked with the libreadline
         library, and when its input is from a terminal, it reads it  using  the
         readline() function. This provides line-editing and history facilities.
-        Note that libreadline is GPL-licenced, so if you distribute a binary of
+        Note that libreadline is GPL-licensed, so if you distribute a binary of
         pcretest linked in this way, there may be licensing issues.
+        Setting  this  option  causes  the -lreadline option to be added to the
+        pcretest build. In many operating environments with  a  sytem-installed
+        libreadline this is sufficient. However, in some environments (e.g.  if
+        an unmodified distribution version of readline is in use),  some  extra
+        configuration  may  be necessary. The INSTALL file for libreadline says
+        this:
+          "Readline uses the termcap functions, but does not link with the
+          termcap or curses library itself, allowing applications which link
+          with readline the to choose an appropriate library."
+        If your environment has not been set up so that an appropriate  library
+        is automatically included, you may need to add something like
+          LIBS="-ncurses"
+        immediately before the configure command.
  SEE ALSO
-Line 558 
 AUTHOR
+Line 594 
 AUTHOR
  REVISION
-        Last updated: 18 December 2007
+        Last updated: 29 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 646 
 THE ALTERNATIVE MATCHING ALGORITHM
+Line 682 
 THE ALTERNATIVE MATCHING ALGORITHM
         though  it is not implemented as a traditional finite state machine (it
         keeps multiple states active simultaneously).
+        Although the general principle of this matching algorithm  is  that  it
+        scans  the subject string only once, without backtracking, there is one
+        exception: when a lookaround assertion is encountered,  the  characters
+        following  or  preceding  the  current  point  have to be independently
+        inspected.
         The scan continues until either the end of the subject is  reached,  or
         there  are  no more unterminated paths. At this point, terminated paths
         represent the different matching possibilities (if there are none,  the
         match  has  failed).   Thus,  if there is more than one possible match,
         this algorithm finds all of them, and in particular, it finds the long-
-        est.  In PCRE, there is an option to stop the algorithm after the first
+        est.  There  is  an  option to stop the algorithm after the first match
-        match (which is necessarily the shortest) has been found.
+        (which is necessarily the shortest) is found.
         Note that all the matches that are found start at the same point in the
         subject. If the pattern
-Line 707 
 THE ALTERNATIVE MATCHING ALGORITHM
+Line 749 
 THE ALTERNATIVE MATCHING ALGORITHM
         tive algorithm moves through the subject  string  one  character  at  a
         time, for all active paths through the tree.
-.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-
+.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
-        ported.
+        are not supported. (*FAIL) is supported, and  behaves  like  a  failing
+        negative assertion.
  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
-        Using the alternative matching algorithm provides the following  advan-
+        Using  the alternative matching algorithm provides the following advan-
         tages:
 . All possible matches (at a single point in the subject) are automat-
-        ically found, and in particular, the longest match is  found.  To  find
+        ically  found,  and  in particular, the longest match is found. To find
         more than one match using the standard algorithm, you have to do kludgy
         things with callouts.
-. There is much better support for partial matching. The  restrictions
+.  Because  the  alternative  algorithm  scans the subject string just
-        on  the content of the pattern that apply when using the standard algo-
+        once, and never needs to backtrack, it is possible to  pass  very  long
-        rithm for partial matching do not apply to the  alternative  algorithm.
+        subject  strings  to  the matching function in several pieces, checking
-        For  non-anchored patterns, the starting position of a partial match is
+        for partial matching each time.  The  pcrepartial  documentation  gives
-        available.
+        details of partial matching.
-. Because the alternative algorithm  scans  the  subject  string  just
-        once,  and  never  needs to backtrack, it is possible to pass very long
-        subject strings to the matching function in  several  pieces,  checking
-        for partial matching each time.
  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
-Line 756 
 AUTHOR
+Line 794 
 AUTHOR
  REVISION
-        Last updated: 08 August 2007
+        Last updated: 29 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 868 
 PCRE API OVERVIEW
+Line 906 
 PCRE API OVERVIEW
         pcre_exec() are used for compiling and matching regular expressions  in
         a  Perl-compatible  manner. A sample program that demonstrates the sim-
         plest way of using them is provided in the file  called  pcredemo.c  in
-        the  source distribution. The pcresample documentation describes how to
+        the PCRE source distribution. A listing of this program is given in the
-        run it.
+        pcredemo documentation, and the pcresample documentation describes  how
+        to compile and run it.
         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
-        ble,  is  also provided. This uses a different algorithm for the match-
+        ble, is also provided. This uses a different algorithm for  the  match-
-        ing. The alternative algorithm finds all possible matches (at  a  given
+        ing.  The  alternative algorithm finds all possible matches (at a given
-        point  in  the subject), and scans the subject just once. However, this
+        point in the subject), and scans the subject just  once  (unless  there
-        algorithm does not return captured substrings. A description of the two
+        are  lookbehind  assertions).  However,  this algorithm does not return
-        matching  algorithms and their advantages and disadvantages is given in
+        captured substrings. A description of the two matching  algorithms  and
-        the pcrematching documentation.
+        their  advantages  and disadvantages is given in the pcrematching docu-
+        mentation.
         In addition to the main compiling and  matching  functions,  there  are
         convenience functions for extracting captured substrings from a subject
-Line 978 
 MULTITHREADING
+Line 1018 
 MULTITHREADING
         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
         callout function pointed to by pcre_callout, are shared by all threads.
-        The compiled form of a regular expression is not altered during  match-
+        The  compiled form of a regular expression is not altered during match-
         ing, so the same compiled pattern can safely be used by several threads
         at once.
-Line 986 
 MULTITHREADING
+Line 1026 
 MULTITHREADING
  SAVING PRECOMPILED PATTERNS FOR LATER USE
         The compiled form of a regular expression can be saved and re-used at a
-        later  time,  possibly by a different program, and even on a host other
+        later time, possibly by a different program, and even on a  host  other
-        than the one on which  it  was  compiled.  Details  are  given  in  the
+        than  the  one  on  which  it  was  compiled.  Details are given in the
-        pcreprecompile  documentation.  However, compiling a regular expression
+        pcreprecompile documentation. However, compiling a  regular  expression
-        with one version of PCRE for use with a different version is not  guar-
+        with  one version of PCRE for use with a different version is not guar-
         anteed to work and may cause crashes.
-Line 997 
 CHECKING BUILD-TIME OPTIONS
+Line 1037 
 CHECKING BUILD-TIME OPTIONS
         int pcre_config(int what, void *where);
-        The  function pcre_config() makes it possible for a PCRE client to dis-
+        The function pcre_config() makes it possible for a PCRE client to  dis-
         cover which optional features have been compiled into the PCRE library.
-        The  pcrebuild documentation has more details about these optional fea-
+        The pcrebuild documentation has more details about these optional  fea-
         tures.
-        The first argument for pcre_config() is an  integer,  specifying  which
+        The  first  argument  for pcre_config() is an integer, specifying which
         information is required; the second argument is a pointer to a variable
-        into which the information is  placed.  The  following  information  is
+        into  which  the  information  is  placed. The following information is
         available:
           PCRE_CONFIG_UTF8
-        The  output is an integer that is set to one if UTF-8 support is avail-
+        The output is an integer that is set to one if UTF-8 support is  avail-
         able; otherwise it is set to zero.
           PCRE_CONFIG_UNICODE_PROPERTIES
-        The output is an integer that is set to  one  if  support  for  Unicode
+        The  output  is  an  integer  that is set to one if support for Unicode
         character properties is available; otherwise it is set to zero.
           PCRE_CONFIG_NEWLINE
-        The  output  is  an integer whose value specifies the default character
+        The output is an integer whose value specifies  the  default  character
-        sequence that is recognized as meaning "newline". The four values  that
+        sequence  that is recognized as meaning "newline". The four values that
         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
-        and -1 for ANY. The default should normally be  the  standard  sequence
+        and  -1  for  ANY.  Though they are derived from ASCII, the same values
-        for your operating system.
+        are returned in EBCDIC environments. The default should normally corre-
+        spond to the standard sequence for your operating system.
           PCRE_CONFIG_BSR
-Line 1050 
 CHECKING BUILD-TIME OPTIONS
+Line 1091 
 CHECKING BUILD-TIME OPTIONS
           PCRE_CONFIG_MATCH_LIMIT
-        The output is an integer that gives the default limit for the number of
+        The output is a long integer that gives the default limit for the  num-
-        internal  matching  function  calls in a pcre_exec() execution. Further
+        ber  of  internal  matching  function calls in a pcre_exec() execution.
-        details are given with pcre_exec() below.
+        Further details are given with pcre_exec() below.
           PCRE_CONFIG_MATCH_LIMIT_RECURSION
-        The output is an integer that gives the default limit for the depth  of
+        The output is a long integer that gives the default limit for the depth
-        recursion  when calling the internal matching function in a pcre_exec()
+        of   recursion  when  calling  the  internal  matching  function  in  a
-        execution. Further details are given with pcre_exec() below.
+        pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
+        below.
           PCRE_CONFIG_STACKRECURSE
-        The output is an integer that is set to one if internal recursion  when
+        The  output is an integer that is set to one if internal recursion when
         running pcre_exec() is implemented by recursive function calls that use
-        the stack to remember their state. This is the usual way that  PCRE  is
+        the  stack  to remember their state. This is the usual way that PCRE is
         compiled. The output is zero if PCRE was compiled to use blocks of data
-        on the  heap  instead  of  recursive  function  calls.  In  this  case,
+        on  the  heap  instead  of  recursive  function  calls.  In  this case,
-        pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
+        pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
         blocks on the heap, thus avoiding the use of the stack.
-Line 1084 
 COMPILING A PATTERN
+Line 1126 
 COMPILING A PATTERN
         Either of the functions pcre_compile() or pcre_compile2() can be called
         to compile a pattern into an internal form. The only difference between
-        the two interfaces is that pcre_compile2() has an additional  argument,
+        the  two interfaces is that pcre_compile2() has an additional argument,
-        errorcodeptr, via which a numerical error code can be returned.
+        errorcodeptr, via which a numerical error  code  can  be  returned.  To
+        avoid  too  much repetition, we refer just to pcre_compile() below, but
+        the information applies equally to pcre_compile2().
         The pattern is a C string terminated by a binary zero, and is passed in
-        the pattern argument. A pointer to a single block  of  memory  that  is
+        the  pattern  argument.  A  pointer to a single block of memory that is
-        obtained  via  pcre_malloc is returned. This contains the compiled code
+        obtained via pcre_malloc is returned. This contains the  compiled  code
         and related data. The pcre type is defined for the returned block; this
         is a typedef for a structure whose contents are not externally defined.
         It is up to the caller to free the memory (via pcre_free) when it is no
         longer required.
-        Although  the compiled code of a PCRE regex is relocatable, that is, it
+        Although the compiled code of a PCRE regex is relocatable, that is,  it
         does not depend on memory location, the complete pcre data block is not
-        fully  relocatable, because it may contain a copy of the tableptr argu-
+        fully relocatable, because it may contain a copy of the tableptr  argu-
         ment, which is an address (see below).
         The options argument contains various bit settings that affect the com-
-        pilation.  It  should be zero if no options are required. The available
+        pilation. It should be zero if no options are required.  The  available
-        options are described below. Some of them, in  particular,  those  that
+        options  are  described  below. Some of them (in particular, those that
-        are  compatible  with  Perl,  can also be set and unset from within the
+        are compatible with Perl, but some others as well) can also be set  and
-        pattern (see the detailed description  in  the  pcrepattern  documenta-
+        unset  from  within  the  pattern  (see the detailed description in the
-        tion).  For  these options, the contents of the options argument speci-
+        pcrepattern documentation). For those options that can be different  in
-        fies their initial settings at the start of compilation and  execution.
+        different  parts  of  the pattern, the contents of the options argument
-        The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time
+        specifies their settings at the start of compilation and execution. The
-        of matching as well as at compile time.
+        PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
+        the time of matching as well as at compile time.
         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
         sets the variable pointed to by errptr to point to a textual error mes-
         sage. This is a static string that is part of the library. You must not
-        try to free it. The offset from the start of the pattern to the charac-
+        try to free it. The byte offset from the start of the  pattern  to  the
-        ter where the error was discovered is placed in the variable pointed to
+        character  that  was  being  processed when the error was discovered is
-        by erroffset, which must not be NULL. If it is, an immediate  error  is
+        placed in the variable pointed to by erroffset, which must not be NULL.
-        given.
+        If  it  is,  an  immediate error is given. Some errors are not detected
+        until checks are carried out when the whole pattern has  been  scanned;
+        in this case the offset is set to the end of the pattern.
         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
         codeptr argument is not NULL, a non-zero error code number is  returned
-Line 1244 
 COMPILING A PATTERN
+Line 1291 
 COMPILING A PATTERN
         before or at the first  newline  in  the  subject  string,  though  the
         matched text may continue over the newline.
+          PCRE_JAVASCRIPT_COMPAT
+        If this option is set, PCRE's behaviour is changed in some ways so that
+        it is compatible with JavaScript rather than Perl. The changes  are  as
+        follows:
+        (1)  A  lone  closing square bracket in a pattern causes a compile-time
+        error, because this is illegal in JavaScript (by default it is  treated
+        as a data character). Thus, the pattern AB]CD becomes illegal when this
+        option is set.
+        (2) At run time, a back reference to an unset subpattern group  matches
+        an  empty  string (by default this causes the current matching alterna-
+        tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
+        set  (assuming  it can find an "a" in the subject), whereas it fails by
+        default, for Perl compatibility.
           PCRE_MULTILINE
-        By  default,  PCRE  treats the subject string as consisting of a single
+        By default, PCRE treats the subject string as consisting  of  a  single
-        line of characters (even if it actually contains newlines). The  "start
+        line  of characters (even if it actually contains newlines). The "start
-        of  line"  metacharacter  (^)  matches only at the start of the string,
+        of line" metacharacter (^) matches only at the  start  of  the  string,
-        while the "end of line" metacharacter ($) matches only at  the  end  of
+        while  the  "end  of line" metacharacter ($) matches only at the end of
         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
         is set). This is the same as Perl.
-        When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
+        When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
-        constructs  match  immediately following or immediately before internal
+        constructs match immediately following or immediately  before  internal
-        newlines in the subject string, respectively, as well as  at  the  very
+        newlines  in  the  subject string, respectively, as well as at the very
-        start  and  end.  This is equivalent to Perl's /m option, and it can be
+        start and end. This is equivalent to Perl's /m option, and  it  can  be
         changed within a pattern by a (?m) option setting. If there are no new-
-        lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
+        lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
         setting PCRE_MULTILINE has no effect.
           PCRE_NEWLINE_CR
-Line 1267 
 COMPILING A PATTERN
+Line 1331 
 COMPILING A PATTERN
           PCRE_NEWLINE_ANYCRLF
           PCRE_NEWLINE_ANY
-        These options override the default newline definition that  was  chosen
+        These  options  override the default newline definition that was chosen
-        when  PCRE  was built. Setting the first or the second specifies that a
+        when PCRE was built. Setting the first or the second specifies  that  a
-        newline is indicated by a single character (CR  or  LF,  respectively).
+        newline  is  indicated  by a single character (CR or LF, respectively).
-        Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
+        Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
-        two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
+        two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
         that any of the three preceding sequences should be recognized. Setting
-        PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
+        PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
         recognized. The Unicode newline sequences are the three just mentioned,
-        plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
+        plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
-        U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
+        U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
-        (paragraph separator, U+2029). The last  two  are  recognized  only  in
+        (paragraph  separator,  U+2029).  The  last  two are recognized only in
         UTF-8 mode.
-        The  newline  setting  in  the  options  word  uses three bits that are
+        The newline setting in the  options  word  uses  three  bits  that  are
         treated as a number, giving eight possibilities. Currently only six are
-        used  (default  plus the five values above). This means that if you set
+        used (default plus the five values above). This means that if  you  set
-        more than one newline option, the combination may or may not be  sensi-
+        more  than one newline option, the combination may or may not be sensi-
         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
-        PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
+        PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
         cause an error.
-        The  only time that a line break is specially recognized when compiling
+        The only time that a line break is specially recognized when  compiling
-        a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
+        a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
-        character  class  is  encountered.  This indicates a comment that lasts
+        character class is encountered. This indicates  a  comment  that  lasts
-        until after the next line break sequence. In other circumstances,  line
+        until  after the next line break sequence. In other circumstances, line
-        break   sequences   are   treated  as  literal  data,  except  that  in
+        break  sequences  are  treated  as  literal  data,   except   that   in
         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
         and are therefore ignored.
         The newline option that is set at compile time becomes the default that
-        is used for pcre_exec() and pcre_dfa_exec(), but it can be  overridden.
+        is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
           PCRE_NO_AUTO_CAPTURE
-Line 1356 
 COMPILATION ERROR CODES
+Line 1420 
 COMPILATION ERROR CODES
  nothing to repeat
  [this code is not in use]
  internal error: unexpected repeat
- unrecognized character after (?
+ unrecognized character after (? or (?-
  POSIX named classes are supported only within a class
  missing )
  reference to non-existent subpattern
-Line 1364 
 COMPILATION ERROR CODES
+Line 1428 
 COMPILATION ERROR CODES
  unknown option bit(s) set
  missing ) after comment
  [this code is not in use]
- regular expression too large
+ regular expression is too large
  failed to get memory
  unmatched parentheses
  internal error: code overflow
-Line 1393 
 COMPILATION ERROR CODES
+Line 1457 
 COMPILATION ERROR CODES
  malformed \P or \p sequence
  unknown property name after \P or \p
  subpattern name is too long (maximum 32 characters)
- too many named subpatterns (maximum 10,000)
+ too many named subpatterns (maximum 10000)
  [this code is not in use]
  octal value is greater than \377 (not in UTF-8 mode)
  internal error: overran compiling workspace
-Line 1402 
 COMPILATION ERROR CODES
+Line 1466 
 COMPILATION ERROR CODES
  DEFINE group contains more than one branch
  repeating a DEFINE group is not allowed
  inconsistent NEWLINE options
- \g is not followed by a braced name or an optionally braced
+ \g is not followed by a braced, angle-bracketed, or quoted
-                non-zero number
+                name/number or by a plain number
- (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
+ a numbered reference must not be zero
+ (*VERB) with an argument is not supported
+ (*VERB) not recognized
+ number is too big
+ subpattern name expected
+ digit expected after (?+
+ ] is an invalid data character in JavaScript compatibility mode
+        The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
+        values may be used if the limits were changed when PCRE was built.
  STUDYING A PATTERN
-Line 1412 
 STUDYING A PATTERN
+Line 1485 
 STUDYING A PATTERN
         pcre_extra *pcre_study(const pcre *code, int options
              const char **errptr);
-        If a compiled pattern is going to be used several times,  it  is  worth
+        If  a  compiled  pattern is going to be used several times, it is worth
         spending more time analyzing it in order to speed up the time taken for
-        matching. The function pcre_study() takes a pointer to a compiled  pat-
+        matching.  The function pcre_study() takes a pointer to a compiled pat-
         tern as its first argument. If studying the pattern produces additional
-        information that will help speed up matching,  pcre_study()  returns  a
+        information  that  will  help speed up matching, pcre_study() returns a
-        pointer  to a pcre_extra block, in which the study_data field points to
+        pointer to a pcre_extra block, in which the study_data field points  to
         the results of the study.
         The  returned  value  from  pcre_study()  can  be  passed  directly  to
-        pcre_exec().  However,  a  pcre_extra  block also contains other fields
+        pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
-        that can be set by the caller before the block  is  passed;  these  are
+        tains  other  fields  that can be set by the caller before the block is
-        described below in the section on matching a pattern.
+        passed; these are described below in the section on matching a pattern.
-        If  studying  the  pattern  does not produce any additional information
+        If studying the  pattern  does  not  produce  any  useful  information,
         pcre_study() returns NULL. In that circumstance, if the calling program
-        wants  to  pass  any of the other fields to pcre_exec(), it must set up
+        wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
-        its own pcre_extra block.
+        pcre_dfa_exec(), it must set up its own pcre_extra block.
-        The second argument of pcre_study() contains option bits.  At  present,
+        The  second  argument of pcre_study() contains option bits. At present,
         no options are defined, and this argument should always be zero.
-        The  third argument for pcre_study() is a pointer for an error message.
+        The third argument for pcre_study() is a pointer for an error  message.
-        If studying succeeds (even if no data is  returned),  the  variable  it
+        If  studying  succeeds  (even  if no data is returned), the variable it
-        points  to  is  set  to NULL. Otherwise it is set to point to a textual
+        points to is set to NULL. Otherwise it is set to  point  to  a  textual
         error message. This is a static string that is part of the library. You
-        must  not  try  to  free it. You should test the error pointer for NULL
+        must not try to free it. You should test the  error  pointer  for  NULL
         after calling pcre_study(), to be sure that it has run successfully.
         This is a typical call to pcre_study():
-Line 1448 
 STUDYING A PATTERN
+Line 1521 
 STUDYING A PATTERN
 ,              /* no options exist */
             &error);        /* set to NULL or points to a message */
-        At present, studying a pattern is useful only for non-anchored patterns
+        Studying a pattern does two things: first, a lower bound for the length
-        that  do not have a single fixed starting character. A bitmap of possi-
+        of subject string that is needed to match the pattern is computed. This
-        ble starting bytes is created.
+        does not mean that there are any strings of that length that match, but
+        it does guarantee that no shorter strings match. The value is  used  by
+        pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
+        match strings that are shorter than the lower bound. You can  find  out
+        the value in a calling program via the pcre_fullinfo() function.
+        Studying a pattern is also useful for non-anchored patterns that do not
+        have a single fixed starting character. A bitmap of  possible  starting
+        bytes  is  created. This speeds up finding a position in the subject at
+        which to start matching.
  LOCALE SUPPORT
-Line 1616 
 INFORMATION ABOUT A PATTERN
+Line 1698 
 INFORMATION ABOUT A PATTERN
         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
         /^a\dz\d/ the returned value is -1.
+          PCRE_INFO_MINLENGTH
+        If the pattern was studied and a minimum length  for  matching  subject
+        strings  was  computed,  its  value is returned. Otherwise the returned
+        value is -1. The value is a number of characters, not bytes  (this  may
+        be  relevant in UTF-8 mode). The fourth argument should point to an int
+        variable. A non-negative value is a lower bound to the  length  of  any
+        matching  string.  There  may not be any strings of that length that do
+        actually match, but every string that does match is at least that long.
           PCRE_INFO_NAMECOUNT
           PCRE_INFO_NAMEENTRYSIZE
           PCRE_INFO_NAMETABLE
-Line 1637 
 INFORMATION ABOUT A PATTERN
+Line 1729 
 INFORMATION ABOUT A PATTERN
         a pointer to the first entry of the table  (a  pointer  to  char).  The
         first two bytes of each entry are the number of the capturing parenthe-
         sis, most significant byte first. The rest of the entry is  the  corre-
-        sponding  name,  zero  terminated. The names are in alphabetical order.
+        sponding name, zero terminated.
-        When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
-        theses  numbers.  For  example,  consider the following pattern (assume
+        The  names are in alphabetical order. Duplicate names may appear if (?|
-        PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
+        is used to create multiple groups with the same number, as described in
-        ignored):
+        the  section  on  duplicate subpattern numbers in the pcrepattern page.
+        Duplicate names for subpatterns with different  numbers  are  permitted
+        only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
+        appear in the table in the order in which they were found in  the  pat-
+        tern.  In  the  absence  of (?| this is the order of increasing number;
+        when (?| is used this is not necessarily the case because later subpat-
+        terns may have lower numbers.
+        As  a  simple  example of the name/number table, consider the following
+        pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
+        lines - is ignored):
           (?<date> (?<year>(\d\d)?\d\d) -
           (?<month>\d\d) - (?<day>\d\d) )
-Line 1662 
 INFORMATION ABOUT A PATTERN
+Line 1764 
 INFORMATION ABOUT A PATTERN
           PCRE_INFO_OKPARTIAL
-        Return 1 if the pattern can be used for partial matching, otherwise  0.
+        Return 1  if  the  pattern  can  be  used  for  partial  matching  with
-        The  fourth  argument  should point to an int variable. The pcrepartial
+        pcre_exec(),  otherwise  0.  The fourth argument should point to an int
-        documentation lists the restrictions that apply to patterns  when  par-
+        variable. From  release  8.00,  this  always  returns  1,  because  the
-        tial matching is used.
+        restrictions  that  previously  applied  to  partial matching have been
+        lifted. The pcrepartial documentation gives details of  partial  match-
+        ing.
           PCRE_INFO_OPTIONS
-Line 1702 
 INFORMATION ABOUT A PATTERN
+Line 1806 
 INFORMATION ABOUT A PATTERN
         Return the size of the data block pointed to by the study_data field in
         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to
         pcre_malloc() when PCRE was getting memory into which to place the data
-        created by pcre_study(). The fourth argument should point to  a  size_t
+        created by pcre_study(). If pcre_extra is NULL, or there  is  no  study
+        data,  zero  is  returned. The fourth argument should point to a size_t
         variable.
-Line 1710 
 OBSOLETE INFO FUNCTION
+Line 1815 
 OBSOLETE INFO FUNCTION
         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
-        The  pcre_info()  function is now obsolete because its interface is too
+        The pcre_info() function is now obsolete because its interface  is  too
-        restrictive to return all the available data about a compiled  pattern.
+        restrictive  to return all the available data about a compiled pattern.
-        New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
+        New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
-        pcre_info() is the number of capturing subpatterns, or one of the  fol-
+        pcre_info()  is the number of capturing subpatterns, or one of the fol-
         lowing negative numbers:
           PCRE_ERROR_NULL       the argument code was NULL
           PCRE_ERROR_BADMAGIC   the "magic number" was not found
-        If  the  optptr  argument is not NULL, a copy of the options with which
+        If the optptr argument is not NULL, a copy of the  options  with  which
-        the pattern was compiled is placed in the integer  it  points  to  (see
+        the  pattern  was  compiled  is placed in the integer it points to (see
         PCRE_INFO_OPTIONS above).
-        If  the  pattern  is  not anchored and the firstcharptr argument is not
+        If the pattern is not anchored and the  firstcharptr  argument  is  not
-        NULL, it is used to pass back information about the first character  of
+        NULL,  it is used to pass back information about the first character of
         any matched string (see PCRE_INFO_FIRSTBYTE above).
-Line 1732 
 REFERENCE COUNTS
+Line 1837 
 REFERENCE COUNTS
         int pcre_refcount(pcre *code, int adjust);
-        The  pcre_refcount()  function is used to maintain a reference count in
+        The pcre_refcount() function is used to maintain a reference  count  in
         the data block that contains a compiled pattern. It is provided for the
-        benefit  of  applications  that  operate  in an object-oriented manner,
+        benefit of applications that  operate  in  an  object-oriented  manner,
         where different parts of the application may be using the same compiled
         pattern, but you want to free the block when they are all done.
         When a pattern is compiled, the reference count field is initialized to
-        zero.  It is changed only by calling this function, whose action is  to
+        zero.   It is changed only by calling this function, whose action is to
-        add  the  adjust  value  (which may be positive or negative) to it. The
+        add the adjust value (which may be positive or  negative)  to  it.  The
         yield of the function is the new value. However, the value of the count
-        is  constrained to lie between 0 and 65535, inclusive. If the new value
+        is constrained to lie between 0 and 65535, inclusive. If the new  value
         is outside these limits, it is forced to the appropriate limit value.
-        Except when it is zero, the reference count is not correctly  preserved
+        Except  when it is zero, the reference count is not correctly preserved
-        if  a  pattern  is  compiled on one host and then transferred to a host
+        if a pattern is compiled on one host and then  transferred  to  a  host
         whose byte-order is different. (This seems a highly unlikely scenario.)
-Line 1758 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1863 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         The  function pcre_exec() is called to match a subject string against a
         compiled pattern, which is passed in the code argument. If the  pattern
-        has been studied, the result of the study should be passed in the extra
+        was  studied,  the  result  of  the study should be passed in the extra
         argument. This function is the main matching facility of  the  library,
         and it operates in a Perl-like manner. For specialist use there is also
         an alternative matching function, which is described below in the  sec-
-Line 1817 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1922 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         The match_limit field provides a means of preventing PCRE from using up
         a  vast amount of resources when running patterns that are not going to
         match, but which have a very large number  of  possibilities  in  their
-        search  trees.  The  classic  example  is  the  use of nested unlimited
+        search  trees. The classic example is a pattern that uses nested unlim-
-        repeats.
+        ited repeats.
         Internally, PCRE uses a function called match() which it calls  repeat-
         edly  (sometimes  recursively). The limit set by match_limit is imposed
-Line 1840 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1945 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         the  total number of calls, because not all calls to match() are recur-
         sive.  This limit is of use only if it is set smaller than match_limit.
-        Limiting  the  recursion  depth  limits the amount of stack that can be
+        Limiting the recursion depth limits the amount of  stack  that  can  be
         used, or, when PCRE has been compiled to use memory on the heap instead
         of the stack, the amount of heap memory that can be used.
-        The  default  value  for  match_limit_recursion can be set when PCRE is
+        The default value for match_limit_recursion can be  set  when  PCRE  is
-        built; the default default  is  the  same  value  as  the  default  for
+        built;  the  default  default  is  the  same  value  as the default for
-        match_limit.  You can override the default by suppling pcre_exec() with
+        match_limit. You can override the default by suppling pcre_exec()  with
-        a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
+        a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
-        PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
+        PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
-        The pcre_callout field is used in conjunction with the  "callout"  fea-
+        The  callout_data  field is used in conjunction with the "callout" fea-
-        ture, which is described in the pcrecallout documentation.
+        ture, and is described in the pcrecallout documentation.
-        The  tables  field  is  used  to  pass  a  character  tables pointer to
+        The tables field  is  used  to  pass  a  character  tables  pointer  to
-        pcre_exec(); this overrides the value that is stored with the  compiled
+        pcre_exec();  this overrides the value that is stored with the compiled
-        pattern.  A  non-NULL value is stored with the compiled pattern only if
+        pattern. A non-NULL value is stored with the compiled pattern  only  if
-        custom tables were supplied to pcre_compile() via  its  tableptr  argu-
+        custom  tables  were  supplied to pcre_compile() via its tableptr argu-
         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
-        PCRE's internal tables to be used. This facility is  helpful  when  re-
+        PCRE's  internal  tables  to be used. This facility is helpful when re-
-        using  patterns  that  have been saved after compiling with an external
+        using patterns that have been saved after compiling  with  an  external
-        set of tables, because the external tables  might  be  at  a  different
+        set  of  tables,  because  the  external tables might be at a different
-        address  when  pcre_exec() is called. See the pcreprecompile documenta-
+        address when pcre_exec() is called. See the  pcreprecompile  documenta-
         tion for a discussion of saving compiled patterns for later use.
     Option bits for pcre_exec()
-        The unused bits of the options argument for pcre_exec() must  be  zero.
+        The  unused  bits of the options argument for pcre_exec() must be zero.
-        The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
+        The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
-        PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
+        PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
-        PCRE_PARTIAL.
+        PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
+        PCRE_PARTIAL_HARD.
           PCRE_ANCHORED
-Line 1950 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2056 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           a?b?
-        is applied to a string not beginning with "a" or "b",  it  matches  the
+        is applied to a string not beginning with "a" or  "b",  it  matches  an
         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
         match is not valid, so PCRE searches further into the string for occur-
         rences of "a" or "b".
-        Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
+          PCRE_NOTEMPTY_ATSTART
-        cial case of a pattern match of the empty  string  within  its  split()
-        function,  and  when  using  the /g modifier. It is possible to emulate
+        This  is  like PCRE_NOTEMPTY, except that an empty string match that is
-        Perl's behaviour after matching a null string by first trying the match
+        not at the start of  the  subject  is  permitted.  If  the  pattern  is
-        again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
+        anchored, such a match can occur only if the pattern contains \K.
-        if that fails by advancing the starting offset (see below)  and  trying
-        an ordinary match again. There is some code that demonstrates how to do
+        Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
-        this in the pcredemo.c sample program.
+        PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
+        match  of  the empty string within its split() function, and when using
+        the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
+        matching a null string by first trying the match again at the same off-
+        set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
+        fails, by advancing the starting offset (see below) and trying an ordi-
+        nary match again. There is some code that demonstrates how to  do  this
+        in the pcredemo sample program.
+          PCRE_NO_START_OPTIMIZE
+        There  are a number of optimizations that pcre_exec() uses at the start
+        of a match, in order to speed up the process. For  example,  if  it  is
+        known  that  a  match must start with a specific character, it searches
+        the subject for that character, and fails immediately if it cannot find
+        it,  without actually running the main matching function. When callouts
+        are in use, these optimizations can cause  them  to  be  skipped.  This
+        option  disables  the  "start-up" optimizations, causing performance to
+        suffer, but ensuring that the callouts do occur.
           PCRE_NO_UTF8_CHECK
-Line 1986 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2110 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         value  of startoffset that does not point to the start of a UTF-8 char-
         acter, is undefined. Your program may crash.
-          PCRE_PARTIAL
+          PCRE_PARTIAL_HARD
+          PCRE_PARTIAL_SOFT
-        This option turns on the  partial  matching  feature.  If  the  subject
+        These options turn on the partial matching feature. For backwards  com-
-        string  fails to match the pattern, but at some point during the match-
+        patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
-        ing process the end of the subject was reached (that  is,  the  subject
+        match occurs if the end of the subject string is reached  successfully,
-        partially  matches  the  pattern and the failure to match occurred only
+        but  there  are not enough subject characters to complete the match. If
-        because there were not enough subject characters), pcre_exec()  returns
+        this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
-        PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
+        returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
-        used, there are restrictions on what may appear in the  pattern.  These
+        matching continues by testing any other alternatives. Only if they  all
-        are discussed in the pcrepartial documentation.
+        fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
+        The portion of the string that was inspected when the partial match was
+        found  is  set  as  the first matching string. There is a more detailed
+        discussion in the pcrepartial documentation.
     The string to be matched by pcre_exec()
-        The  subject string is passed to pcre_exec() as a pointer in subject, a
+        The subject string is passed to pcre_exec() as a pointer in subject,  a
-        length in length, and a starting byte offset in startoffset.  In  UTF-8
+        length (in bytes) in length, and a starting byte offset in startoffset.
-        mode,  the  byte  offset  must point to the start of a UTF-8 character.
+        In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
-        Unlike the pattern string, the subject may contain binary  zero  bytes.
+        acter.  Unlike  the pattern string, the subject may contain binary zero
-        When  the starting offset is zero, the search for a match starts at the
+        bytes. When the starting offset is zero, the search for a match  starts
-        beginning of the subject, and this is by far the most common case.
+        at  the  beginning  of  the subject, and this is by far the most common
+        case.
         A non-zero starting offset is useful when searching for  another  match
         in  the same subject by calling pcre_exec() again after a previous suc-
-Line 2040 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2169 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         string.  PCRE  supports several other kinds of parenthesized subpattern
         that do not cause substrings to be captured.
-        Captured substrings are returned to the caller via a vector of  integer
+        Captured substrings are returned to the caller via a vector of integers
-        offsets  whose  address is passed in ovector. The number of elements in
+        whose  address is passed in ovector. The number of elements in the vec-
-        the vector is passed in ovecsize, which must be a non-negative  number.
+        tor is passed in ovecsize, which must be a non-negative  number.  Note:
-        Note: this argument is NOT the size of ovector in bytes.
+        this argument is NOT the size of ovector in bytes.
         The  first  two-thirds of the vector is used to pass back captured sub-
         strings, each substring using a pair of integers. The  remaining  third
         of  the  vector is used as workspace by pcre_exec() while matching cap-
         turing subpatterns, and is not available for passing back  information.
-        The  length passed in ovecsize should always be a multiple of three. If
+        The  number passed in ovecsize should always be a multiple of three. If
         it is not, it is rounded down.
         When a match is successful, information about  captured  substrings  is
         returned  in  pairs  of integers, starting at the beginning of ovector,
         and continuing up to two-thirds of its length at the  most.  The  first
-        element of a pair is set to the offset of the first character in a sub-
+        element  of  each pair is set to the byte offset of the first character
-        string, and the second is set to the  offset  of  the  first  character
+        in a substring, and the second is set to the byte offset of  the  first
-        after  the  end  of  a  substring. The first pair, ovector[0] and ovec-
+        character  after  the end of a substring. Note: these values are always
-        tor[1], identify the portion of  the  subject  string  matched  by  the
+        byte offsets, even in UTF-8 mode. They are not character counts.
-        entire  pattern.  The next pair is used for the first capturing subpat-
-        tern, and so on. The value returned by pcre_exec() is one more than the
+        The first pair of integers, ovector[0]  and  ovector[1],  identify  the
-        highest numbered pair that has been set. For example, if two substrings
+        portion  of  the subject string matched by the entire pattern. The next
-        have been captured, the returned value is 3. If there are no  capturing
+        pair is used for the first capturing subpattern, and so on.  The  value
-        subpatterns,  the return value from a successful match is 1, indicating
+        returned by pcre_exec() is one more than the highest numbered pair that
-        that just the first pair of offsets has been set.
+        has been set.  For example, if two substrings have been  captured,  the
+        returned  value is 3. If there are no capturing subpatterns, the return
+        value from a successful match is 1, indicating that just the first pair
+        of offsets has been set.
         If a capturing subpattern is matched repeatedly, it is the last portion
         of the string that it matched that is returned.
-        If  the vector is too small to hold all the captured substring offsets,
+        If the vector is too small to hold all the captured substring  offsets,
         it is used as far as possible (up to two-thirds of its length), and the
-        function  returns a value of zero. In particular, if the substring off-
+        function returns a value of zero. If the substring offsets are  not  of
-        sets are not of interest, pcre_exec() may be called with ovector passed
+        interest,  pcre_exec()  may  be  called with ovector passed as NULL and
-        as  NULL  and  ovecsize  as zero. However, if the pattern contains back
+        ovecsize as zero. However, if the pattern contains back references  and
-        references and the ovector is not big enough to  remember  the  related
+        the  ovector is not big enough to remember the related substrings, PCRE
-        substrings,  PCRE has to get additional memory for use during matching.
+        has to get additional memory for use during matching. Thus it  is  usu-
-        Thus it is usually advisable to supply an ovector.
+        ally advisable to supply an ovector.
-        The pcre_info() function can be used to find  out  how  many  capturing
+        The pcre_fullinfo() function can be used to find out how many capturing
-        subpatterns  there  are  in  a  compiled pattern. The smallest size for
+        subpatterns there are in a compiled  pattern.  The  smallest  size  for
-        ovector that will allow for n captured substrings, in addition  to  the
+        ovector  that  will allow for n captured substrings, in addition to the
         offsets of the substring matched by the whole pattern, is (n+1)*3.
-        It  is  possible for capturing subpattern number n+1 to match some part
+        It is possible for capturing subpattern number n+1 to match  some  part
         of the subject when subpattern n has not been used at all. For example,
-        if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
+        if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
         return from the function is 4, and subpatterns 1 and 3 are matched, but
- is  not.  When  this happens, both values in the offset pairs corre-
+is not. When this happens, both values in  the  offset  pairs  corre-
         sponding to unused subpatterns are set to -1.
-        Offset values that correspond to unused subpatterns at the end  of  the
+        Offset  values  that correspond to unused subpatterns at the end of the
-        expression  are  also  set  to  -1. For example, if the string "abc" is
+        expression are also set to -1. For example,  if  the  string  "abc"  is
-        matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
+        matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
-        matched.  The  return  from the function is 2, because the highest used
+        matched. The return from the function is 2, because  the  highest  used
         capturing subpattern number is 1. However, you can refer to the offsets
-        for  the  second  and third capturing subpatterns if you wish (assuming
+        for the second and third capturing subpatterns if  you  wish  (assuming
         the vector is large enough, of course).
-        Some convenience functions are provided  for  extracting  the  captured
+        Some  convenience  functions  are  provided for extracting the captured
         substrings as separate strings. These are described below.
     Error return values from pcre_exec()
-        If  pcre_exec()  fails, it returns a negative number. The following are
+        If pcre_exec() fails, it returns a negative number. The  following  are
         defined in the header file:
           PCRE_ERROR_NOMATCH        (-1)
-Line 2112 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2244 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_ERROR_NULL           (-2)
-        Either code or subject was passed as NULL,  or  ovector  was  NULL  and
+        Either  code  or  subject  was  passed as NULL, or ovector was NULL and
         ovecsize was not zero.
           PCRE_ERROR_BADOPTION      (-3)
-Line 2121 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2253 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_ERROR_BADMAGIC       (-4)
-        PCRE  stores a 4-byte "magic number" at the start of the compiled code,
+        PCRE stores a 4-byte "magic number" at the start of the compiled  code,
         to catch the case when it is passed a junk pointer and to detect when a
         pattern that was compiled in an environment of one endianness is run in
-        an environment with the other endianness. This is the error  that  PCRE
+        an  environment  with the other endianness. This is the error that PCRE
         gives when the magic number is not present.
           PCRE_ERROR_UNKNOWN_OPCODE (-5)
         While running the pattern match, an unknown item was encountered in the
-        compiled pattern. This error could be caused by a bug  in  PCRE  or  by
+        compiled  pattern.  This  error  could be caused by a bug in PCRE or by
         overwriting of the compiled pattern.
           PCRE_ERROR_NOMEMORY       (-6)
-        If  a  pattern contains back references, but the ovector that is passed
+        If a pattern contains back references, but the ovector that  is  passed
         to pcre_exec() is not big enough to remember the referenced substrings,
-        PCRE  gets  a  block of memory at the start of matching to use for this
+        PCRE gets a block of memory at the start of matching to  use  for  this
-        purpose. If the call via pcre_malloc() fails, this error is given.  The
+        purpose.  If the call via pcre_malloc() fails, this error is given. The
         memory is automatically freed at the end of matching.
           PCRE_ERROR_NOSUBSTRING    (-7)
-        This  error is used by the pcre_copy_substring(), pcre_get_substring(),
+        This error is used by the pcre_copy_substring(),  pcre_get_substring(),
         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
         returned by pcre_exec().
           PCRE_ERROR_MATCHLIMIT     (-8)
-        The  backtracking  limit,  as  specified  by the match_limit field in a
+        The backtracking limit, as specified by  the  match_limit  field  in  a
-        pcre_extra structure (or defaulted) was reached.  See  the  description
+        pcre_extra  structure  (or  defaulted) was reached. See the description
         above.
           PCRE_ERROR_CALLOUT        (-9)
         This error is never generated by pcre_exec() itself. It is provided for
-        use by callout functions that want to yield a distinctive  error  code.
+        use  by  callout functions that want to yield a distinctive error code.
         See the pcrecallout documentation for details.
           PCRE_ERROR_BADUTF8        (-10)
-        A  string  that contains an invalid UTF-8 byte sequence was passed as a
+        A string that contains an invalid UTF-8 byte sequence was passed  as  a
         subject.
           PCRE_ERROR_BADUTF8_OFFSET (-11)
         The UTF-8 byte sequence that was passed as a subject was valid, but the
-        value  of startoffset did not point to the beginning of a UTF-8 charac-
+        value of startoffset did not point to the beginning of a UTF-8  charac-
         ter.
           PCRE_ERROR_PARTIAL        (-12)
-        The subject string did not match, but it did match partially.  See  the
+        The  subject  string did not match, but it did match partially. See the
         pcrepartial documentation for details of partial matching.
           PCRE_ERROR_BADPARTIAL     (-13)
-        The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
+        This code is no longer in  use.  It  was  formerly  returned  when  the
-        items that are not supported for partial matching. See the  pcrepartial
+        PCRE_PARTIAL  option  was used with a compiled pattern containing items
-        documentation for details of partial matching.
+        that were  not  supported  for  partial  matching.  From  release  8.00
+        onwards, there are no restrictions on partial matching.
           PCRE_ERROR_INTERNAL       (-14)
-Line 2188 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2321 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_ERROR_BADCOUNT       (-15)
-        This error is given if the value of the ovecsize argument is  negative.
+        This error is given if the value of the ovecsize argument is negative.
           PCRE_ERROR_RECURSIONLIMIT (-21)
         The internal recursion limit, as specified by the match_limit_recursion
-        field in a pcre_extra structure (or defaulted)  was  reached.  See  the
+        field  in  a  pcre_extra  structure (or defaulted) was reached. See the
         description above.
           PCRE_ERROR_BADNEWLINE     (-23)
-Line 2216 
 EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
+Line 2349 
 EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
         int pcre_get_substring_list(const char *subject,
              int *ovector, int stringcount, const char ***listptr);
-        Captured  substrings  can  be  accessed  directly  by using the offsets
+        Captured substrings can be  accessed  directly  by  using  the  offsets
-        returned by pcre_exec() in  ovector.  For  convenience,  the  functions
+        returned  by  pcre_exec()  in  ovector.  For convenience, the functions
         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
-        string_list() are provided for extracting captured substrings  as  new,
+        string_list()  are  provided for extracting captured substrings as new,
-        separate,  zero-terminated strings. These functions identify substrings
+        separate, zero-terminated strings. These functions identify  substrings
-        by number. The next section describes functions  for  extracting  named
+        by  number.  The  next section describes functions for extracting named
         substrings.
-        A  substring that contains a binary zero is correctly extracted and has
+        A substring that contains a binary zero is correctly extracted and  has
-        a further zero added on the end, but the result is not, of course, a  C
+        a  further zero added on the end, but the result is not, of course, a C
-        string.   However,  you  can  process such a string by referring to the
+        string.  However, you can process such a string  by  referring  to  the
-        length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
+        length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
         string().  Unfortunately, the interface to pcre_get_substring_list() is
-        not adequate for handling strings containing binary zeros, because  the
+        not  adequate for handling strings containing binary zeros, because the
         end of the final string is not independently indicated.
-        The  first  three  arguments  are the same for all three of these func-
+        The first three arguments are the same for all  three  of  these  func-
-        tions: subject is the subject string that has  just  been  successfully
+        tions:  subject  is  the subject string that has just been successfully
         matched, ovector is a pointer to the vector of integer offsets that was
         passed to pcre_exec(), and stringcount is the number of substrings that
-        were  captured  by  the match, including the substring that matched the
+        were captured by the match, including the substring  that  matched  the
         entire regular expression. This is the value returned by pcre_exec() if
-        it  is greater than zero. If pcre_exec() returned zero, indicating that
+        it is greater than zero. If pcre_exec() returned zero, indicating  that
-        it ran out of space in ovector, the value passed as stringcount  should
+        it  ran out of space in ovector, the value passed as stringcount should
         be the number of elements in the vector divided by three.
-        The  functions pcre_copy_substring() and pcre_get_substring() extract a
+        The functions pcre_copy_substring() and pcre_get_substring() extract  a
-        single substring, whose number is given as  stringnumber.  A  value  of
+        single  substring,  whose  number  is given as stringnumber. A value of
-        zero  extracts  the  substring that matched the entire pattern, whereas
+        zero extracts the substring that matched the  entire  pattern,  whereas
-        higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
+        higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
-        string(),  the  string  is  placed  in buffer, whose length is given by
+        string(), the string is placed in buffer,  whose  length  is  given  by
-        buffersize, while for pcre_get_substring() a new  block  of  memory  is
+        buffersize,  while  for  pcre_get_substring()  a new block of memory is
-        obtained  via  pcre_malloc,  and its address is returned via stringptr.
+        obtained via pcre_malloc, and its address is  returned  via  stringptr.
-        The yield of the function is the length of the  string,  not  including
+        The  yield  of  the function is the length of the string, not including
         the terminating zero, or one of these error codes:
           PCRE_ERROR_NOMEMORY       (-6)
-        The  buffer  was too small for pcre_copy_substring(), or the attempt to
+        The buffer was too small for pcre_copy_substring(), or the  attempt  to
         get memory failed for pcre_get_substring().
           PCRE_ERROR_NOSUBSTRING    (-7)
         There is no substring whose number is stringnumber.
-        The pcre_get_substring_list()  function  extracts  all  available  sub-
+        The  pcre_get_substring_list()  function  extracts  all  available sub-
-        strings  and  builds  a list of pointers to them. All this is done in a
+        strings and builds a list of pointers to them. All this is  done  in  a
         single block of memory that is obtained via pcre_malloc. The address of
-        the  memory  block  is returned via listptr, which is also the start of
+        the memory block is returned via listptr, which is also  the  start  of
-        the list of string pointers. The end of the list is marked  by  a  NULL
+        the  list  of  string pointers. The end of the list is marked by a NULL
-        pointer.  The  yield  of  the function is zero if all went well, or the
+        pointer. The yield of the function is zero if all  went  well,  or  the
         error code
           PCRE_ERROR_NOMEMORY       (-6)
         if the attempt to get the memory block failed.
-        When any of these functions encounter a substring that is unset,  which
+        When  any of these functions encounter a substring that is unset, which
-        can  happen  when  capturing subpattern number n+1 matches some part of
+        can happen when capturing subpattern number n+1 matches  some  part  of
-        the subject, but subpattern n has not been used at all, they return  an
+        the  subject, but subpattern n has not been used at all, they return an
         empty string. This can be distinguished from a genuine zero-length sub-
-        string by inspecting the appropriate offset in ovector, which is  nega-
+        string  by inspecting the appropriate offset in ovector, which is nega-
         tive for unset substrings.
-        The  two convenience functions pcre_free_substring() and pcre_free_sub-
+        The two convenience functions pcre_free_substring() and  pcre_free_sub-
-        string_list() can be used to free the memory  returned  by  a  previous
+        string_list()  can  be  used  to free the memory returned by a previous
         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
-        tively. They do nothing more than  call  the  function  pointed  to  by
+        tively.  They  do  nothing  more  than  call the function pointed to by
-        pcre_free,  which  of course could be called directly from a C program.
+        pcre_free, which of course could be called directly from a  C  program.
-        However, PCRE is used in some situations where it is linked via a  spe-
+        However,  PCRE is used in some situations where it is linked via a spe-
-        cial   interface  to  another  programming  language  that  cannot  use
+        cial  interface  to  another  programming  language  that  cannot   use
-        pcre_free directly; it is for these cases that the functions  are  pro-
+        pcre_free  directly;  it is for these cases that the functions are pro-
         vided.
-Line 2306 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
+Line 2439 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
              int stringcount, const char *stringname,
              const char **stringptr);
-        To  extract a substring by name, you first have to find associated num-
+        To extract a substring by name, you first have to find associated  num-
         ber.  For example, for this pattern
           (a+)b(?<xxx>\d+)...
-Line 2315 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
+Line 2448 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
         be unique (PCRE_DUPNAMES was not set), you can find the number from the
         name by calling pcre_get_stringnumber(). The first argument is the com-
         piled pattern, and the second is the name. The yield of the function is
-        the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
+        the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no
         subpattern of that name.
         Given the number, you can extract the substring directly, or use one of
         the functions described in the previous section. For convenience, there
         are also two functions that do the whole job.
-        Most    of    the    arguments   of   pcre_copy_named_substring()   and
+        Most   of   the   arguments    of    pcre_copy_named_substring()    and
-        pcre_get_named_substring() are the same  as  those  for  the  similarly
+        pcre_get_named_substring()  are  the  same  as  those for the similarly
-        named  functions  that extract by number. As these are described in the
+        named functions that extract by number. As these are described  in  the
-        previous section, they are not re-described here. There  are  just  two
+        previous  section,  they  are not re-described here. There are just two
         differences:
-        First,  instead  of a substring number, a substring name is given. Sec-
+        First, instead of a substring number, a substring name is  given.  Sec-
         ond, there is an extra argument, given at the start, which is a pointer
-        to  the compiled pattern. This is needed in order to gain access to the
+        to the compiled pattern. This is needed in order to gain access to  the
         name-to-number translation table.
-        These functions call pcre_get_stringnumber(), and if it succeeds,  they
+        These  functions call pcre_get_stringnumber(), and if it succeeds, they
-        then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
+        then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
-        ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
+        ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
         behaviour may not be what you want (see the next section).
+        Warning: If the pattern uses the (?| feature to set up multiple subpat-
+        terns  with  the  same number, as described in the section on duplicate
+        subpattern numbers in the pcrepattern page, you  cannot  use  names  to
+        distinguish  the  different subpatterns, because names are not included
+        in the compiled code. The matching process uses only numbers. For  this
+        reason,  the  use of different names for subpatterns of the same number
+        causes an error at compile time.
  DUPLICATE SUBPATTERN NAMES
         int pcre_get_stringtable_entries(const pcre *code,
              const char *name, char **first, char **last);
-        When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
+        When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
-        subpatterns are not required to  be  unique.  Normally,  patterns  with
+        subpatterns  are not required to be unique. (Duplicate names are always
-        duplicate  names  are such that in any one match, only one of the named
+        allowed for subpatterns with the same number, created by using the  (?|
-        subpatterns participates. An example is shown in the pcrepattern  docu-
+        feature.  Indeed,  if  such subpatterns are named, they are required to
-        mentation.
+        use the same names.)
-        When    duplicates   are   present,   pcre_copy_named_substring()   and
+        Normally, patterns with duplicate names are such that in any one match,
-        pcre_get_named_substring() return the first substring corresponding  to
+        only  one of the named subpatterns participates. An example is shown in
-        the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
+        the pcrepattern documentation.
-        (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
-        function  returns one of the numbers that are associated with the name,
+        When   duplicates   are   present,   pcre_copy_named_substring()    and
+        pcre_get_named_substring()  return the first substring corresponding to
+        the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
+        (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
+        function returns one of the numbers that are associated with the  name,
         but it is not defined which it is.
-        If you want to get full details of all captured substrings for a  given
+        If  you want to get full details of all captured substrings for a given
-        name,  you  must  use  the pcre_get_stringtable_entries() function. The
+        name, you must use  the  pcre_get_stringtable_entries()  function.  The
         first argument is the compiled pattern, and the second is the name. The
-        third  and  fourth  are  pointers to variables which are updated by the
+        third and fourth are pointers to variables which  are  updated  by  the
         function. After it has run, they point to the first and last entries in
-        the  name-to-number  table  for  the  given  name.  The function itself
+        the name-to-number table  for  the  given  name.  The  function  itself
-        returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
+        returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
-        there  are none. The format of the table is described above in the sec-
+        there are none. The format of the table is described above in the  sec-
-        tion entitled Information about a  pattern.   Given  all  the  relevant
+        tion  entitled  Information  about  a  pattern.  Given all the relevant
-        entries  for the name, you can extract each of their numbers, and hence
+        entries for the name, you can extract each of their numbers, and  hence
         the captured data, if any.
  FINDING ALL POSSIBLE MATCHES
-        The traditional matching function uses a  similar  algorithm  to  Perl,
+        The  traditional  matching  function  uses a similar algorithm to Perl,
         which stops when it finds the first match, starting at a given point in
-        the subject. If you want to find all possible matches, or  the  longest
+        the  subject.  If you want to find all possible matches, or the longest
-        possible  match,  consider using the alternative matching function (see
+        possible match, consider using the alternative matching  function  (see
-        below) instead. If you cannot use the alternative function,  but  still
+        below)  instead.  If you cannot use the alternative function, but still
-        need  to  find all possible matches, you can kludge it up by making use
+        need to find all possible matches, you can kludge it up by  making  use
         of the callout facility, which is described in the pcrecallout documen-
         tation.
         What you have to do is to insert a callout right at the end of the pat-
-        tern.  When your callout function is called, extract and save the  cur-
+        tern.   When your callout function is called, extract and save the cur-
-        rent  matched  substring.  Then  return  1, which forces pcre_exec() to
+        rent matched substring. Then return  1,  which  forces  pcre_exec()  to
-        backtrack and try other alternatives. Ultimately, when it runs  out  of
+        backtrack  and  try other alternatives. Ultimately, when it runs out of
         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
-Line 2395 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2540 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
              int options, int *ovector, int ovecsize,
              int *workspace, int wscount);
-        The  function  pcre_dfa_exec()  is  called  to  match  a subject string
+        The function pcre_dfa_exec()  is  called  to  match  a  subject  string
-        against a compiled pattern, using a matching algorithm that  scans  the
+        against  a  compiled pattern, using a matching algorithm that scans the
-        subject  string  just  once, and does not backtrack. This has different
+        subject string just once, and does not backtrack.  This  has  different
-        characteristics to the normal algorithm, and  is  not  compatible  with
+        characteristics  to  the  normal  algorithm, and is not compatible with
-        Perl.  Some  of the features of PCRE patterns are not supported. Never-
+        Perl. Some of the features of PCRE patterns are not  supported.  Never-
-        theless, there are times when this kind of matching can be useful.  For
+        theless,  there are times when this kind of matching can be useful. For
-        a discussion of the two matching algorithms, see the pcrematching docu-
+        a discussion of the two matching algorithms, and  a  list  of  features
-        mentation.
+        that  pcre_dfa_exec() does not support, see the pcrematching documenta-
+        tion.
         The arguments for the pcre_dfa_exec() function  are  the  same  as  for
         pcre_exec(), plus two extras. The ovector argument is used in a differ-
-Line 2437 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2583 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
         The unused bits of the options argument  for  pcre_dfa_exec()  must  be
         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-
-        LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
+        LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
-        PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
+        PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
-        three of these are the same as for pcre_exec(), so their description is
+        TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last
-        not repeated here.
+        four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
+        description is not repeated here.
-          PCRE_PARTIAL
+          PCRE_PARTIAL_HARD
-        This  has  the  same general effect as it does for pcre_exec(), but the
+          PCRE_PARTIAL_SOFT
-        details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for
-        pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into
+        These have the same general effect as they do for pcre_exec(), but  the
-        PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have
+        details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
-        been no complete matches, but there is still at least one matching pos-
+        pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
-        sibility. The portion of the string that provided the partial match  is
+        ject  is  reached  and there is still at least one matching possibility
-        set as the first matching string.
+        that requires additional characters. This happens even if some complete
+        matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
+        code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
+        of  the  subject  is  reached, there have been no complete matches, but
+        there is still at least one matching possibility. The  portion  of  the
+        string  that  was inspected when the longest partial match was found is
+        set as the first matching string in both cases.
           PCRE_DFA_SHORTEST
-        Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
+        Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
         stop as soon as it has found one match. Because of the way the alterna-
-        tive  algorithm  works, this is necessarily the shortest possible match
+        tive algorithm works, this is necessarily the shortest  possible  match
         at the first possible matching point in the subject string.
           PCRE_DFA_RESTART
-        When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and
+        When pcre_dfa_exec() returns a partial match, it is possible to call it
-        returns  a  partial  match, it is possible to call it again, with addi-
+        again, with additional subject characters, and have  it  continue  with
-        tional subject characters, and have it continue with  the  same  match.
+        the  same match. The PCRE_DFA_RESTART option requests this action; when
-        The  PCRE_DFA_RESTART  option requests this action; when it is set, the
+        it is set, the workspace and wscount options must  reference  the  same
-        workspace and wscount options must reference the same vector as  before
+        vector  as  before  because data about the match so far is left in them
-        because  data  about  the  match so far is left in them after a partial
+        after a partial match. There is more discussion of this facility in the
-        match. There is more discussion of this  facility  in  the  pcrepartial
+        pcrepartial documentation.
-        documentation.
     Successful returns from pcre_dfa_exec()
-Line 2545 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2696 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
  SEE ALSO
         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
-        tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
+        tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
  AUTHOR
-Line 2557 
 AUTHOR
+Line 2708 
 AUTHOR
  REVISION
-        Last updated: 27 November 2007
+        Last updated: 03 October 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2587 
 PCRE CALLOUTS
+Line 2738 
 PCRE CALLOUTS
           (?C1)abc(?C2)def
-        If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
+        If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
-        called, PCRE automatically  inserts  callouts,  all  with  number  255,
+        pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
-        before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is
+        with  number  255,  before  each  item  in the pattern. For example, if
-        used with the pattern
+        PCRE_AUTO_CALLOUT is used with the pattern
           A(\d{2}|--)
-Line 2609 
 PCRE CALLOUTS
+Line 2760 
 PCRE CALLOUTS
  MISSING CALLOUTS
         You  should  be  aware  that,  because of optimizations in the way PCRE
-        matches patterns, callouts sometimes do not happen. For example, if the
+        matches patterns by default, callouts  sometimes  do  not  happen.  For
-        pattern is
+        example, if the pattern is
           ab(?C4)cd
-Line 2619 
 MISSING CALLOUTS
+Line 2770 
 MISSING CALLOUTS
         ever  start,  and  the  callout is never reached. However, with "abyd",
         though the result is still no match, the callout is obeyed.
+        If the pattern is studied, PCRE knows the minimum length of a  matching
+        string,  and will immediately give a "no match" return without actually
+        running a match if the subject is not long enough, or,  for  unanchored
+        patterns, if it has been scanned far enough.
+        You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
+        MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
+        matching  process,  but  does  ensure that callouts such as the example
+        above are obeyed.
  THE CALLOUT INTERFACE
-Line 2646 
 THE CALLOUT INTERFACE
+Line 2807 
 THE CALLOUT INTERFACE
         version number will change again in future  if  additional  fields  are
         added, but the intention is never to remove any of the existing fields.
-        The callout_number field contains the number of the  callout,  as  com-
+        The  callout_number  field  contains the number of the callout, as com-
-        piled  into  the pattern (that is, the number after ?C for manual call-
+        piled into the pattern (that is, the number after ?C for  manual  call-
         outs, and 255 for automatically generated callouts).
-        The offset_vector field is a pointer to the vector of offsets that  was
+        The  offset_vector field is a pointer to the vector of offsets that was
-        passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
+        passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
-        pcre_exec() is used, the contents can be inspected in order to  extract
+        pcre_exec()  is used, the contents can be inspected in order to extract
-        substrings  that  have  been  matched  so  far,  in the same way as for
+        substrings that have been matched so  far,  in  the  same  way  as  for
-        extracting substrings after a match has completed. For  pcre_dfa_exec()
+        extracting  substrings after a match has completed. For pcre_dfa_exec()
         this field is not useful.
         The subject and subject_length fields contain copies of the values that
         were passed to pcre_exec().
-        The start_match field normally contains the offset within  the  subject
+        The  start_match  field normally contains the offset within the subject
-        at  which  the  current  match  attempt started. However, if the escape
+        at which the current match attempt  started.  However,  if  the  escape
-        sequence \K has been encountered, this value is changed to reflect  the
+        sequence  \K has been encountered, this value is changed to reflect the
-        modified  starting  point.  If the pattern is not anchored, the callout
+        modified starting point. If the pattern is not  anchored,  the  callout
         function may be called several times from the same point in the pattern
         for different starting points in the subject.
-        The  current_position  field  contains the offset within the subject of
+        The current_position field contains the offset within  the  subject  of
         the current match pointer.
-        When the pcre_exec() function is used, the capture_top  field  contains
+        When  the  pcre_exec() function is used, the capture_top field contains
-        one  more than the number of the highest numbered captured substring so
+        one more than the number of the highest numbered captured substring  so
-        far. If no substrings have been captured, the value of  capture_top  is
+        far.  If  no substrings have been captured, the value of capture_top is
-        one.  This  is always the case when pcre_dfa_exec() is used, because it
+        one. This is always the case when pcre_dfa_exec() is used,  because  it
         does not support captured substrings.
-        The capture_last field contains the number of the  most  recently  cap-
+        The  capture_last  field  contains the number of the most recently cap-
-        tured  substring. If no substrings have been captured, its value is -1.
+        tured substring. If no substrings have been captured, its value is  -1.
         This is always the case when pcre_dfa_exec() is used.
-        The callout_data field contains a value that is passed  to  pcre_exec()
+        The  callout_data  field contains a value that is passed to pcre_exec()
-        or  pcre_dfa_exec() specifically so that it can be passed back in call-
+        or pcre_dfa_exec() specifically so that it can be passed back in  call-
-        outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
+        outs.  It  is  passed  in the pcre_callout field of the pcre_extra data
-        structure.  If  no such data was passed, the value of callout_data in a
+        structure. If no such data was passed, the value of callout_data  in  a
-        pcre_callout block is NULL. There is a description  of  the  pcre_extra
+        pcre_callout  block  is  NULL. There is a description of the pcre_extra
         structure in the pcreapi documentation.
-        The  pattern_position field is present from version 1 of the pcre_call-
+        The pattern_position field is present from version 1 of the  pcre_call-
         out structure. It contains the offset to the next item to be matched in
         the pattern string.
-        The  next_item_length field is present from version 1 of the pcre_call-
+        The next_item_length field is present from version 1 of the  pcre_call-
         out structure. It contains the length of the next item to be matched in
-        the  pattern  string. When the callout immediately precedes an alterna-
+        the pattern string. When the callout immediately precedes  an  alterna-
-        tion bar, a closing parenthesis, or the end of the pattern, the  length
+        tion  bar, a closing parenthesis, or the end of the pattern, the length
-        is  zero.  When the callout precedes an opening parenthesis, the length
+        is zero. When the callout precedes an opening parenthesis,  the  length
         is that of the entire subpattern.
-        The pattern_position and next_item_length fields are intended  to  help
+        The  pattern_position  and next_item_length fields are intended to help
-        in  distinguishing between different automatic callouts, which all have
+        in distinguishing between different automatic callouts, which all  have
         the same callout number. However, they are set for all callouts.
  RETURN VALUES
-        The external callout function returns an integer to PCRE. If the  value
+        The  external callout function returns an integer to PCRE. If the value
-        is  zero,  matching  proceeds  as  normal. If the value is greater than
+        is zero, matching proceeds as normal. If  the  value  is  greater  than
-        zero, matching fails at the current point, but  the  testing  of  other
+        zero,  matching  fails  at  the current point, but the testing of other
         matching possibilities goes ahead, just as if a lookahead assertion had
-        failed. If the value is less than zero, the  match  is  abandoned,  and
+        failed.  If  the  value  is less than zero, the match is abandoned, and
-        pcre_exec() (or pcre_dfa_exec()) returns the negative value.
+        pcre_exec() or pcre_dfa_exec() returns the negative value.
-        Negative   values   should   normally   be   chosen  from  the  set  of
+        Negative  values  should  normally  be   chosen   from   the   set   of
         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
-        dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
+        dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
-        reserved for use by callout functions; it will never be  used  by  PCRE
+        reserved  for  use  by callout functions; it will never be used by PCRE
         itself.
-Line 2728 
 AUTHOR
+Line 2889 
 AUTHOR
  REVISION
-        Last updated: 29 May 2007
+        Last updated: 29 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2743 
 NAME
+Line 2904 
 NAME
  DIFFERENCES BETWEEN PCRE AND PERL
         This  document describes the differences in the ways that PCRE and Perl
-        handle regular expressions. The differences described here  are  mainly
+        handle regular expressions. The differences  described  here  are  with
-        with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
+        respect to Perl 5.10.
-        some features that are expected to be in the forthcoming Perl 5.10.
-. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
+.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
-        of  what  it does have are given in the section on UTF-8 support in the
+        of what it does have are given in the section on UTF-8 support  in  the
         main pcre page.
 . PCRE does not allow repeat quantifiers on lookahead assertions. Perl
-        permits  them,  but they do not mean what you might think. For example,
+        permits them, but they do not mean what you might think.  For  example,
         (?!a){3} does not assert that the next three characters are not "a". It
         just asserts that the next character is not "a" three times.
-.  Capturing  subpatterns  that occur inside negative lookahead asser-
+. Capturing subpatterns that occur inside  negative  lookahead  asser-
-        tions are counted, but their entries in the offsets  vector  are  never
+        tions  are  counted,  but their entries in the offsets vector are never
-        set.  Perl sets its numerical variables from any such patterns that are
+        set. Perl sets its numerical variables from any such patterns that  are
         matched before the assertion fails to match something (thereby succeed-
-        ing),  but  only  if the negative lookahead assertion contains just one
+        ing), but only if the negative lookahead assertion  contains  just  one
         branch.
-. Though binary zero characters are supported in the  subject  string,
+.  Though  binary zero characters are supported in the subject string,
         they are not allowed in a pattern string because it is passed as a nor-
         mal C string, terminated by zero. The escape sequence \0 can be used in
         the pattern to represent a binary zero.
-.  The  following Perl escape sequences are not supported: \l, \u, \L,
+. The following Perl escape sequences are not supported: \l,  \u,  \L,
         \U, and \N. In fact these are implemented by Perl's general string-han-
-        dling  and are not part of its pattern matching engine. If any of these
+        dling and are not part of its pattern matching engine. If any of  these
         are encountered by PCRE, an error is generated.
-. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
+.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
-        is  built  with Unicode character property support. The properties that
+        is built with Unicode character property support. The  properties  that
-        can be tested with \p and \P are limited to the general category  prop-
+        can  be tested with \p and \P are limited to the general category prop-
-        erties  such  as  Lu and Nd, script names such as Greek or Han, and the
+        erties such as Lu and Nd, script names such as Greek or  Han,  and  the
-        derived properties Any and L&.
+        derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
+        property, which Perl does not; the  Perl  documentation  says  "Because
+        Perl hides the need for the user to understand the internal representa-
+        tion of Unicode characters, there is no need to implement the  somewhat
+        messy concept of surrogates."
 . PCRE does support the \Q...\E escape for quoting substrings. Charac-
-        ters  in  between  are  treated as literals. This is slightly different
+        ters in between are treated as literals.  This  is  slightly  different
-        from Perl in that $ and @ are  also  handled  as  literals  inside  the
+        from  Perl  in  that  $  and  @ are also handled as literals inside the
-        quotes.  In Perl, they cause variable interpolation (but of course PCRE
+        quotes. In Perl, they cause variable interpolation (but of course  PCRE
         does not have variables). Note the following examples:
             Pattern            PCRE matches      Perl matches
-Line 2792 
 DIFFERENCES BETWEEN PCRE AND PERL
+Line 2956 
 DIFFERENCES BETWEEN PCRE AND PERL
             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
-        The \Q...\E sequence is recognized both inside  and  outside  character
+        The  \Q...\E  sequence  is recognized both inside and outside character
         classes.
 . Fairly obviously, PCRE does not support the (?{code}) and (??{code})
-        constructions. However, there is support for recursive  patterns.  This
+        constructions.  However,  there is support for recursive patterns. This
-        is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE
+        is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
-        "callout" feature allows an external function to be called during  pat-
+        "callout"  feature allows an external function to be called during pat-
         tern matching. See the pcrecallout documentation for details.
-.  Subpatterns  that  are  called  recursively or as "subroutines" are
+. Subpatterns that are called  recursively  or  as  "subroutines"  are
-        always treated as atomic groups in  PCRE.  This  is  like  Python,  but
+        always  treated  as  atomic  groups  in  PCRE. This is like Python, but
-        unlike Perl.
+        unlike Perl. There is a discussion of an example that explains this  in
+        more  detail  in  the section on recursion differences from Perl in the
-.  There are some differences that are concerned with the settings of
+        pcrepattern page.
-        captured strings when part of  a  pattern  is  repeated.  For  example,
-        matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
+. There are some differences that are concerned with the settings  of
+        captured  strings  when  part  of  a  pattern is repeated. For example,
+        matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
         unset, but in PCRE it is set to "b".
 .  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
-        (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
+        (*FAIL), (*F), (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but  only  in
-        the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
+        the forms without an argument. PCRE does not support (*MARK).
-        (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
-        ture group; this is different to Perl.
+.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
+        pattern names is not as general as Perl's. This is a consequence of the
-. PCRE provides some extensions to the Perl regular expression facil-
+        fact the PCRE works internally just with numbers, using an external ta-
-        ities.   Perl  5.10  will  include new features that are not in earlier
+        ble to translate between numbers and names. In  particular,  a  pattern
-        versions, some of which (such as named parentheses) have been  in  PCRE
+        such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
-        for some time. This list is with respect to Perl 5.10:
+        the same number but different names, is not supported,  and  causes  an
+        error  at compile time. If it were allowed, it would not be possible to
-        (a)  Although  lookbehind  assertions  must match fixed length strings,
+        distinguish which parentheses matched, because both names map  to  cap-
-        each alternative branch of a lookbehind assertion can match a different
+        turing subpattern number 1. To avoid this confusing situation, an error
-        length of string. Perl requires them all to have the same length.
+        is given at compile time.
+. PCRE provides some extensions to the Perl regular expression facil-
+        ities.   Perl  5.10  includes new features that are not in earlier ver-
+        sions of Perl, some of which (such as named parentheses) have  been  in
+        PCRE for some time. This list is with respect to Perl 5.10:
+        (a)  Although  lookbehind  assertions  in  PCRE must match fixed length
+        strings, each alternative branch of a lookbehind assertion can match  a
+        different  length  of  string.  Perl requires them all to have the same
+        length.
-        (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
+        (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $
         meta-character matches only at the very end of the string.
         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
         ignored.  (Perl can be made to issue a warning.)
-        (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
+        (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-
         fiers is inverted, that is, by default they are not greedy, but if fol-
         lowed by a question mark they are.
         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
         tried only at the first matching position in the subject string.
-        (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
+        (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
-        TURE options for pcre_exec() have no Perl equivalents.
+        and  PCRE_NO_AUTO_CAPTURE  options for pcre_exec() have no Perl equiva-
+        lents.
         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
         CRLF by the PCRE_BSR_ANYCRLF option.
-Line 2869 
 AUTHOR
+Line 3046 
 AUTHOR
  REVISION
-        Last updated: 11 September 2007
+        Last updated: 04 October 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2885 
 PCRE REGULAR EXPRESSION DETAILS
+Line 3062 
 PCRE REGULAR EXPRESSION DETAILS
         The  syntax and semantics of the regular expressions that are supported
         by PCRE are described in detail below. There is a quick-reference  syn-
-        tax  summary  in  the  pcresyntax  page. Perl's regular expressions are
+        tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
-        described in its own documentation, and regular expressions in  general
+        semantics as closely as it can. PCRE  also  supports  some  alternative
-        are  covered in a number of books, some of which have copious examples.
+        regular  expression  syntax (which does not conflict with the Perl syn-
-        Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by
+        tax) in order to provide some compatibility with regular expressions in
-        O'Reilly,  covers regular expressions in great detail. This description
+        Python, .NET, and Oniguruma.
-        of PCRE's regular expressions is intended as reference material.
+        Perl's  regular expressions are described in its own documentation, and
+        regular expressions in general are covered in a number of  books,  some
+        of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
+        Expressions", published by  O'Reilly,  covers  regular  expressions  in
+        great  detail.  This  description  of  PCRE's  regular  expressions  is
+        intended as reference material.
         The original operation of PCRE was on strings of  one-byte  characters.
         However,  there is now also support for UTF-8 character strings. To use
-        this, you must build PCRE to  include  UTF-8  support,  and  then  call
+        this, PCRE must be built to include UTF-8 support, and  you  must  call
-        pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern
+        pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
-        matching is mentioned in several places below. There is also a  summary
+        also a special sequence that can be given at the start of a pattern:
-        of  UTF-8  features  in  the  section on UTF-8 support in the main pcre
-        page.
+          (*UTF8)
+        Starting a pattern with this sequence  is  equivalent  to  setting  the
+        PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
+        UTF-8 mode affects pattern matching  is  mentioned  in  several  places
+        below.  There  is  also  a  summary of UTF-8 features in the section on
+        UTF-8 support in the main pcre page.
         The remainder of this document discusses the  patterns  that  are  sup-
         ported  by  PCRE when its main matching function, pcre_exec(), is used.
-Line 2928 
 NEWLINE CONVENTIONS
+Line 3117 
 NEWLINE CONVENTIONS
           (*ANYCRLF)   any of the three above
           (*ANY)       all Unicode newline sequences
-        These override the default and the options given to pcre_compile(). For
+        These  override  the default and the options given to pcre_compile() or
-        example, on a Unix system where LF is the default newline sequence, the
+        pcre_compile2(). For example, on a Unix system where LF is the  default
-        pattern
+        newline sequence, the pattern
           (*CR)a.b
-Line 3002 
 CHARACTERS AND METACHARACTERS
+Line 3191 
 CHARACTERS AND METACHARACTERS
                    syntax)
           ]      terminates the character class
-        The  following sections describe the use of each of the metacharacters.
+        The following sections describe the use of each of the metacharacters.
  BACKSLASH
         The backslash character has several uses. Firstly, if it is followed by
-        a  non-alphanumeric  character,  it takes away any special meaning that
+        a non-alphanumeric character, it takes away any  special  meaning  that
-        character may have. This  use  of  backslash  as  an  escape  character
+        character  may  have.  This  use  of  backslash  as an escape character
         applies both inside and outside character classes.
-        For  example,  if  you want to match a * character, you write \* in the
+        For example, if you want to match a * character, you write  \*  in  the
-        pattern.  This escaping action applies whether  or  not  the  following
+        pattern.   This  escaping  action  applies whether or not the following
-        character  would  otherwise be interpreted as a metacharacter, so it is
+        character would otherwise be interpreted as a metacharacter, so  it  is
-        always safe to precede a non-alphanumeric  with  backslash  to  specify
+        always  safe  to  precede  a non-alphanumeric with backslash to specify
-        that  it stands for itself. In particular, if you want to match a back-
+        that it stands for itself. In particular, if you want to match a  back-
         slash, you write \\.
-        If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
+        If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
-        the  pattern (other than in a character class) and characters between a
+        the pattern (other than in a character class) and characters between  a
         # outside a character class and the next newline are ignored. An escap-
-        ing  backslash  can  be  used to include a whitespace or # character as
+        ing backslash can be used to include a whitespace  or  #  character  as
         part of the pattern.
-        If you want to remove the special meaning from a  sequence  of  charac-
+        If  you  want  to remove the special meaning from a sequence of charac-
-        ters,  you can do so by putting them between \Q and \E. This is differ-
+        ters, you can do so by putting them between \Q and \E. This is  differ-
-        ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
+        ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E
-        sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
+        sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
         tion. Note the following examples:
           Pattern            PCRE matches   Perl matches
-Line 3038 
 BACKSLASH
+Line 3227 
 BACKSLASH
           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
-        The \Q...\E sequence is recognized both inside  and  outside  character
+        The  \Q...\E  sequence  is recognized both inside and outside character
         classes.
     Non-printing characters
         A second use of backslash provides a way of encoding non-printing char-
-        acters in patterns in a visible manner. There is no restriction on  the
+        acters  in patterns in a visible manner. There is no restriction on the
-        appearance  of non-printing characters, apart from the binary zero that
+        appearance of non-printing characters, apart from the binary zero  that
-        terminates a pattern, but when a pattern  is  being  prepared  by  text
+        terminates  a  pattern,  but  when  a pattern is being prepared by text
-        editing,  it  is  usually  easier  to  use  one of the following escape
+        editing, it is  often  easier  to  use  one  of  the  following  escape
         sequences than the binary character it represents:
           \a        alarm, that is, the BEL character (hex 07)
-Line 3061 
 BACKSLASH
+Line 3250 
 BACKSLASH
           \xhh      character with hex code hh
           \x{hhh..} character with hex code hhh..
-        The precise effect of \cx is as follows: if x is a lower  case  letter,
+        The  precise  effect of \cx is as follows: if x is a lower case letter,
-        it  is converted to upper case. Then bit 6 of the character (hex 40) is
+        it is converted to upper case. Then bit 6 of the character (hex 40)  is
-        inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;
+        inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
         becomes hex 7B.
-        After  \x, from zero to two hexadecimal digits are read (letters can be
+        After \x, from zero to two hexadecimal digits are read (letters can  be
-        in upper or lower case). Any number of hexadecimal  digits  may  appear
+        in  upper  or  lower case). Any number of hexadecimal digits may appear
-        between  \x{  and  },  but the value of the character code must be less
+        between \x{ and }, but the value of the character  code  must  be  less
         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
-        the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
+        the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
         than the largest Unicode code point, which is 10FFFF.
-        If characters other than hexadecimal digits appear between \x{  and  },
+        If  characters  other than hexadecimal digits appear between \x{ and },
         or if there is no terminating }, this form of escape is not recognized.
-        Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
+        Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
-        escape,  with  no  following  digits, giving a character whose value is
+        escape, with no following digits, giving a  character  whose  value  is
         zero.
         Characters whose value is less than 256 can be defined by either of the
-        two  syntaxes  for  \x. There is no difference in the way they are han-
+        two syntaxes for \x. There is no difference in the way  they  are  han-
         dled. For example, \xdc is exactly the same as \x{dc}.
-        After \0 up to two further octal digits are read. If  there  are  fewer
+        After  \0  up  to two further octal digits are read. If there are fewer
-        than  two  digits,  just  those  that  are  present  are used. Thus the
+        than two digits, just  those  that  are  present  are  used.  Thus  the
         sequence \0\x\07 specifies two binary zeros followed by a BEL character
-        (code  value 7). Make sure you supply two digits after the initial zero
+        (code value 7). Make sure you supply two digits after the initial  zero
         if the pattern character that follows is itself an octal digit.
         The handling of a backslash followed by a digit other than 0 is compli-
         cated.  Outside a character class, PCRE reads it and any following dig-
-        its as a decimal number. If the number is less than  10,  or  if  there
+        its  as  a  decimal  number. If the number is less than 10, or if there
         have been at least that many previous capturing left parentheses in the
-        expression, the entire  sequence  is  taken  as  a  back  reference.  A
+        expression,  the  entire  sequence  is  taken  as  a  back reference. A
-        description  of how this works is given later, following the discussion
+        description of how this works is given later, following the  discussion
         of parenthesized subpatterns.
-        Inside a character class, or if the decimal number is  greater  than  9
+        Inside  a  character  class, or if the decimal number is greater than 9
-        and  there have not been that many capturing subpatterns, PCRE re-reads
+        and there have not been that many capturing subpatterns, PCRE  re-reads
         up to three octal digits following the backslash, and uses them to gen-
-        erate  a data character. Any subsequent digits stand for themselves. In
+        erate a data character. Any subsequent digits stand for themselves.  In
-        non-UTF-8 mode, the value of a character specified  in  octal  must  be
+        non-UTF-8  mode,  the  value  of a character specified in octal must be
-        less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
+        less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For
         example:
           \040   is another way of writing a space
-Line 3120 
 BACKSLASH
+Line 3309 
 BACKSLASH
           \81    is either a back reference, or a binary zero
                     followed by the two characters "8" and "1"
-        Note that octal values of 100 or greater must not be  introduced  by  a
+        Note  that  octal  values of 100 or greater must not be introduced by a
         leading zero, because no more than three octal digits are ever read.
         All the sequences that define a single character value can be used both
-        inside and outside character classes. In addition, inside  a  character
+        inside  and  outside character classes. In addition, inside a character
-        class,  the  sequence \b is interpreted as the backspace character (hex
+        class, the sequence \b is interpreted as the backspace  character  (hex
-), and the sequences \R and \X are interpreted as the characters  "R"
+),  and the sequences \R and \X are interpreted as the characters "R"
-        and  "X", respectively. Outside a character class, these sequences have
+        and "X", respectively. Outside a character class, these sequences  have
         different meanings (see below).
     Absolute and relative back references
-        The sequence \g followed by an unsigned or a negative  number,  option-
+        The  sequence  \g followed by an unsigned or a negative number, option-
-        ally  enclosed  in braces, is an absolute or relative back reference. A
+        ally enclosed in braces, is an absolute or relative back  reference.  A
         named back reference can be coded as \g{name}. Back references are dis-
         cussed later, following the discussion of parenthesized subpatterns.
+    Absolute and relative subroutine calls
+        For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
+        name or a number enclosed either in angle brackets or single quotes, is
+        an alternative syntax for referencing a subpattern as  a  "subroutine".
+        Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
+        \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
+        reference; the latter is a subroutine call.
     Generic character types
         Another use of backslash is for specifying generic character types. The
-Line 3172 
 BACKSLASH
+Line 3370 
 BACKSLASH
         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
         code  character  property  support is available. These sequences retain
         their original meanings from before UTF-8 support was available, mainly
-        for efficiency reasons.
+        for  efficiency  reasons. Note that this also affects \b, because it is
+        defined in terms of \w and \W.
         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
-        the other sequences, these do match certain high-valued  codepoints  in
+        the  other  sequences, these do match certain high-valued codepoints in
         UTF-8 mode.  The horizontal space characters are:
           U+0009     Horizontal tab
-Line 3209 
 BACKSLASH
+Line 3408 
 BACKSLASH
           U+2029     Paragraph separator
         A "word" character is an underscore or any character less than 256 that
-        is a letter or digit. The definition of  letters  and  digits  is  con-
+        is  a  letter  or  digit.  The definition of letters and digits is con-
-        trolled  by PCRE's low-valued character tables, and may vary if locale-
+        trolled by PCRE's low-valued character tables, and may vary if  locale-
-        specific matching is taking place (see "Locale support" in the  pcreapi
+        specific  matching is taking place (see "Locale support" in the pcreapi
-        page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
+        page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
-        systems, or "french" in Windows, some character codes greater than  128
+        systems,  or "french" in Windows, some character codes greater than 128
-        are  used for accented letters, and these are matched by \w. The use of
+        are used for accented letters, and these are matched by \w. The use  of
         locales with Unicode is discouraged.
     Newline sequences
-        Outside a character class, by default, the escape sequence  \R  matches
+        Outside  a  character class, by default, the escape sequence \R matches
         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
         mode \R is equivalent to the following:
           (?>\r\n|\n|\x0b|\f|\r|\x85)
-        This is an example of an "atomic group", details  of  which  are  given
+        This  is  an  example  of an "atomic group", details of which are given
         below.  This particular group matches either the two-character sequence
-        CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
+        CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
         return, U+000D), or NEL (next line, U+0085). The two-character sequence
         is treated as a single unit that cannot be split.
-        In  UTF-8  mode, two additional characters whose codepoints are greater
+        In UTF-8 mode, two additional characters whose codepoints  are  greater
         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
-        rator,  U+2029).   Unicode character property support is not needed for
+        rator, U+2029).  Unicode character property support is not  needed  for
         these characters to be recognized.
         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
-        the  complete  set  of  Unicode  line  endings)  by  setting the option
+        the complete set  of  Unicode  line  endings)  by  setting  the  option
         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
         (BSR is an abbrevation for "backslash R".) This can be made the default
-        when PCRE is built; if this is the case, the  other  behaviour  can  be
+        when  PCRE  is  built;  if this is the case, the other behaviour can be
-        requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
+        requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
-        specify these settings by starting a pattern string  with  one  of  the
+        specify  these  settings  by  starting a pattern string with one of the
         following sequences:
           (*BSR_ANYCRLF)   CR, LF, or CRLF only
           (*BSR_UNICODE)   any Unicode newline sequence
-        These override the default and the options given to pcre_compile(), but
+        These override the default and the options given to  pcre_compile()  or
-        they can be overridden by options given to pcre_exec(). Note that these
+        pcre_compile2(),  but  they  can  be  overridden  by  options  given to
-        special settings, which are not Perl-compatible, are recognized only at
+        pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
-        the very start of a pattern, and that they must be in  upper  case.  If
+        are  not  Perl-compatible,  are  recognized only at the very start of a
-        more  than  one  of  them is present, the last one is used. They can be
+        pattern, and that they must be in upper case. If more than one of  them
-        combined with a change of newline convention, for  example,  a  pattern
+        is present, the last one is used. They can be combined with a change of
-        can start with:
+        newline convention, for example, a pattern can start with:
           (*ANY)(*BSR_ANYCRLF)
-Line 3264 
 BACKSLASH
+Line 3463 
 BACKSLASH
     Unicode character properties
         When PCRE is built with Unicode character property support, three addi-
-        tional escape sequences that match characters with specific  properties
+        tional  escape sequences that match characters with specific properties
-        are  available.   When not in UTF-8 mode, these sequences are of course
+        are available.  When not in UTF-8 mode, these sequences are  of  course
-        limited to testing characters whose codepoints are less than  256,  but
+        limited  to  testing characters whose codepoints are less than 256, but
         they do work in this mode.  The extra escape sequences are:
           \p{xx}   a character with the xx property
           \P{xx}   a character without the xx property
           \X       an extended Unicode sequence
-        The  property  names represented by xx above are limited to the Unicode
+        The property names represented by xx above are limited to  the  Unicode
         script names, the general category properties, and "Any", which matches
         any character (including newline). Other properties such as "InMusical-
-        Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does
+        Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
         not match any characters, so always causes a match failure.
         Sets of Unicode characters are defined as belonging to certain scripts.
-        A character from one of these sets can be matched using a script  name.
+        A  character from one of these sets can be matched using a script name.
         For example:
           \p{Greek}
           \P{Han}
-        Those  that are not part of an identified script are lumped together as
+        Those that are not part of an identified script are lumped together  as
         "Common". The current list of scripts is:
         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
-        Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,
+        Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
-        Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-
+        Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
-        gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,
+        gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
-        Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,
+        Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
-        Each character has exactly one general category property, specified  by
+        Each  character has exactly one general category property, specified by
         a two-letter abbreviation. For compatibility with Perl, negation can be
-        specified by including a circumflex between the opening brace  and  the
+        specified  by  including a circumflex between the opening brace and the
         property name. For example, \p{^Lu} is the same as \P{Lu}.
         If only one letter is specified with \p or \P, it includes all the gen-
-        eral category properties that start with that letter. In this case,  in
+        eral  category properties that start with that letter. In this case, in
-        the  absence of negation, the curly brackets in the escape sequence are
+        the absence of negation, the curly brackets in the escape sequence  are
         optional; these two examples have the same effect:
           \p{L}
-Line 3358 
 BACKSLASH
+Line 3557 
 BACKSLASH
           Zp    Paragraph separator
           Zs    Space separator
-        The special property L& is also supported: it matches a character  that
+        The  special property L& is also supported: it matches a character that
-        has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
+        has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
         classified as a modifier or "other".
-        The Cs (Surrogate) property applies only to  characters  in  the  range
+        The  Cs  (Surrogate)  property  applies only to characters in the range
-        U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
+        U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
-        ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
+        ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
-        the pcreapi page).
+        the pcreapi page). Perl does not support the Cs property.
-        The long synonyms for these properties  that  Perl  supports  (such  as
+        The  long  synonyms  for  property  names  that  Perl supports (such as
-        \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
+        \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
         any of these properties with "Is".
         No character that is in the Unicode table has the Cn (unassigned) prop-
         erty.  Instead, this property is assumed for any code point that is not
         in the Unicode table.
-        Specifying caseless matching does not affect  these  escape  sequences.
+        Specifying  caseless  matching  does not affect these escape sequences.
         For example, \p{Lu} always matches only upper case letters.
-        The  \X  escape  matches  any number of Unicode characters that form an
+        The \X escape matches any number of Unicode  characters  that  form  an
         extended Unicode sequence. \X is equivalent to
           (?>\PM\pM*)
-        That is, it matches a character without the "mark"  property,  followed
+        That  is,  it matches a character without the "mark" property, followed
-        by  zero  or  more  characters with the "mark" property, and treats the
+        by zero or more characters with the "mark"  property,  and  treats  the
-        sequence as an atomic group (see below).  Characters  with  the  "mark"
+        sequence  as  an  atomic group (see below).  Characters with the "mark"
-        property  are  typically  accents  that affect the preceding character.
+        property are typically accents that  affect  the  preceding  character.
-        None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
+        None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
         matches any one character.
-        Matching  characters  by Unicode property is not fast, because PCRE has
+        Matching characters by Unicode property is not fast, because  PCRE  has
-        to search a structure that contains  data  for  over  fifteen  thousand
+        to  search  a  structure  that  contains data for over fifteen thousand
         characters. That is why the traditional escape sequences such as \d and
         \w do not use Unicode properties in PCRE.
     Resetting the match start
         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
-        ously  matched  characters  not  to  be  included  in the final matched
+        ously matched characters not  to  be  included  in  the  final  matched
         sequence. For example, the pattern:
           foo\Kbar
-        matches "foobar", but reports that it has matched "bar".  This  feature
+        matches  "foobar",  but reports that it has matched "bar". This feature
-        is  similar  to  a lookbehind assertion (described below).  However, in
+        is similar to a lookbehind assertion (described  below).   However,  in
-        this case, the part of the subject before the real match does not  have
+        this  case, the part of the subject before the real match does not have
-        to  be of fixed length, as lookbehind assertions do. The use of \K does
+        to be of fixed length, as lookbehind assertions do. The use of \K  does
-        not interfere with the setting of captured  substrings.   For  example,
+        not  interfere  with  the setting of captured substrings.  For example,
         when the pattern
           (foo)\Kbar
-Line 3417 
 BACKSLASH
+Line 3616 
 BACKSLASH
     Simple assertions
-        The  final use of backslash is for certain simple assertions. An asser-
+        The final use of backslash is for certain simple assertions. An  asser-
-        tion specifies a condition that has to be met at a particular point  in
+        tion  specifies a condition that has to be met at a particular point in
-        a  match, without consuming any characters from the subject string. The
+        a match, without consuming any characters from the subject string.  The
-        use of subpatterns for more complicated assertions is described  below.
+        use  of subpatterns for more complicated assertions is described below.
         The backslashed assertions are:
           \b     matches at a word boundary
-Line 3431 
 BACKSLASH
+Line 3630 
 BACKSLASH
           \z     matches only at the end of the subject
           \G     matches at the first matching position in the subject
-        These  assertions may not appear in character classes (but note that \b
+        These assertions may not appear in character classes (but note that  \b
         has a different meaning, namely the backspace character, inside a char-
         acter class).
-        A  word  boundary is a position in the subject string where the current
+        A word boundary is a position in the subject string where  the  current
-        character and the previous character do not both match \w or  \W  (i.e.
+        character  and  the previous character do not both match \w or \W (i.e.
-        one  matches  \w  and the other matches \W), or the start or end of the
+        one matches \w and the other matches \W), or the start or  end  of  the
-        string if the first or last character matches \w, respectively.
+        string if the first or last character matches \w, respectively. Neither
+        PCRE nor Perl has a separte "start of word" or "end  of  word"  metase-
+        quence.  However,  whatever follows \b normally determines which it is.
+        For example, the fragment \ba matches "a" at the start of a word.
         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
         and dollar (described in the next section) in that they only ever match
-Line 3564 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3766 
 SQUARE BRACKETS AND CHARACTER CLASSES
         An opening square bracket introduces a character class, terminated by a
         closing square bracket. A closing square bracket on its own is not spe-
-        cial. If a closing square bracket is required as a member of the class,
+        cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
-        it  should  be  the first data character in the class (after an initial
+        a lone closing square bracket causes a compile-time error. If a closing
-        circumflex, if present) or escaped with a backslash.
+        square bracket is required as a member of the class, it should  be  the
+        first  data  character  in  the  class (after an initial circumflex, if
+        present) or escaped with a backslash.
         A character class matches a single character in the subject.  In  UTF-8
-        mode,  the character may occupy more than one byte. A matched character
+        mode, the character may be more than one byte long. A matched character
         must be in the set of characters defined by the class, unless the first
         character  in  the  class definition is a circumflex, in which case the
         subject character must not be in the set defined by  the  class.  If  a
-Line 3580 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3784 
 SQUARE BRACKETS AND CHARACTER CLASSES
         while  [^aeiou]  matches  any character that is not a lower case vowel.
         Note that a circumflex is just a convenient notation for specifying the
         characters  that  are in the class by enumerating those that are not. A
-        class that starts with a circumflex is not an assertion: it still  con-
+        class that starts with a circumflex is not an assertion; it still  con-
         sumes  a  character  from the subject string, and therefore it fails if
         the current pointer is at the end of the string.
-Line 3596 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3800 
 SQUARE BRACKETS AND CHARACTER CLASSES
         than  128, so caseless matching is always possible. For characters with
         higher values, the concept of case is supported  if  PCRE  is  compiled
         with  Unicode  property support, but not otherwise.  If you want to use
-        caseless matching for characters 128 and above, you  must  ensure  that
+        caseless matching in UTF8-mode for characters 128 and above,  you  must
-        PCRE  is  compiled  with Unicode property support as well as with UTF-8
+        ensure  that  PCRE is compiled with Unicode property support as well as
-        support.
+        with UTF-8 support.
         Characters that might indicate line breaks are  never  treated  in  any
         special  way  when  matching  character  classes,  whatever line-ending
-Line 3698 
 POSIX CHARACTER CLASSES
+Line 3902 
 POSIX CHARACTER CLASSES
  VERTICAL BAR
-        Vertical bar characters are used to separate alternative patterns.  For
+        Vertical  bar characters are used to separate alternative patterns. For
         example, the pattern
           gilbert|sullivan
-        matches  either "gilbert" or "sullivan". Any number of alternatives may
+        matches either "gilbert" or "sullivan". Any number of alternatives  may
-        appear, and an empty  alternative  is  permitted  (matching  the  empty
+        appear,  and  an  empty  alternative  is  permitted (matching the empty
         string). The matching process tries each alternative in turn, from left
-        to right, and the first one that succeeds is used. If the  alternatives
+        to  right, and the first one that succeeds is used. If the alternatives
-        are  within a subpattern (defined below), "succeeds" means matching the
+        are within a subpattern (defined below), "succeeds" means matching  the
-        rest of the main pattern as well as the alternative in the  subpattern.
+        rest of the main pattern as well as the alternative in the subpattern.
  INTERNAL OPTION SETTING
-Line 3734 
 INTERNAL OPTION SETTING
+Line 3938 
 INTERNAL OPTION SETTING
         can be changed in the same way as the Perl-compatible options by  using
         the characters J, U and X respectively.
-        When  an option change occurs at top level (that is, not inside subpat-
+        When  one  of  these  option  changes occurs at top level (that is, not
-        tern parentheses), the change applies to the remainder of  the  pattern
+        inside subpattern parentheses), the change applies to the remainder  of
-        that follows.  If the change is placed right at the start of a pattern,
+        the pattern that follows. If the change is placed right at the start of
-        PCRE extracts it into the global options (and it will therefore show up
+        a pattern, PCRE extracts it into the global options (and it will there-
-        in data extracted by the pcre_fullinfo() function).
+        fore show up in data extracted by the pcre_fullinfo() function).
         An  option  change  within a subpattern (see below for a description of
         subpatterns) affects only that part of the current pattern that follows
-Line 3761 
 INTERNAL OPTION SETTING
+Line 3965 
 INTERNAL OPTION SETTING
         Note: There are other PCRE-specific options that  can  be  set  by  the
         application  when  the  compile  or match functions are called. In some
-        cases the pattern can contain special  leading  sequences  to  override
+        cases the pattern can contain special leading sequences such as (*CRLF)
-        what  the  application  has set or what has been defaulted. Details are
+        to  override  what  the application has set or what has been defaulted.
-        given in the section entitled "Newline sequences" above.
+        Details are given in the section entitled  "Newline  sequences"  above.
+        There  is  also  the  (*UTF8)  leading sequence that can be used to set
+        UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
  SUBPATTERNS
-Line 3845 
 DUPLICATE SUBPATTERN NUMBERS
+Line 4051 
 DUPLICATE SUBPATTERN NUMBERS
           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
           # 1            2         2  3        2     3     4
-        A  backreference  or  a  recursive call to a numbered subpattern always
+        A  backreference  to  a  numbered subpattern uses the most recent value
-        refers to the first one in the pattern with the given number.
+        that is set for that number by any subpattern.  The  following  pattern
+        matches "abcabc" or "defdef":
+          /(?|(abc)|(def))\1/
+        In  contrast, a recursive or "subroutine" call to a numbered subpattern
+        always refers to the first one in the pattern with  the  given  number.
+        The following pattern matches "abcabc" or "defabc":
+          /(?|(abc)|(def))(?1)/
-        An alternative approach to using this "branch reset" feature is to  use
+        If  a condition test for a subpattern's having matched refers to a non-
+        unique number, the test is true if any of the subpatterns of that  num-
+        ber have matched.
+        An  alternative approach to using this "branch reset" feature is to use
         duplicate named subpatterns, as described in the next section.
  NAMED SUBPATTERNS
-        Identifying  capturing  parentheses  by number is simple, but it can be
+        Identifying capturing parentheses by number is simple, but  it  can  be
-        very hard to keep track of the numbers in complicated  regular  expres-
+        very  hard  to keep track of the numbers in complicated regular expres-
-        sions.  Furthermore,  if  an  expression  is  modified, the numbers may
+        sions. Furthermore, if an  expression  is  modified,  the  numbers  may
-        change. To help with this difficulty, PCRE supports the naming of  sub-
+        change.  To help with this difficulty, PCRE supports the naming of sub-
         patterns. This feature was not added to Perl until release 5.10. Python
-        had the feature earlier, and PCRE introduced it at release  4.0,  using
+        had  the  feature earlier, and PCRE introduced it at release 4.0, using
-        the  Python syntax. PCRE now supports both the Perl and the Python syn-
+        the Python syntax. PCRE now supports both the Perl and the Python  syn-
-        tax.
+        tax.  Perl  allows  identically  numbered subpatterns to have different
+        names, but PCRE does not.
         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)
         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References
-Line 3878 
 NAMED SUBPATTERNS
+Line 4098 
 NAMED SUBPATTERNS
         By  default, a name must be unique within a pattern, but it is possible
         to relax this constraint by setting the PCRE_DUPNAMES option at compile
-        time.  This  can  be useful for patterns where only one instance of the
+        time.  (Duplicate  names are also always permitted for subpatterns with
+        the same number, set up as described in the previous  section.)  Dupli-
+        cate  names  can  be useful for patterns where only one instance of the
         named parentheses can match. Suppose you want to match the  name  of  a
         weekday,  either as a 3-letter abbreviation or as the full name, and in
         both cases you want to extract the abbreviation. This pattern (ignoring
-Line 3897 
 NAMED SUBPATTERNS
+Line 4119 
 NAMED SUBPATTERNS
         The  convenience  function  for extracting the data by name returns the
         substring for the first (and in this example, the only)  subpattern  of
         that  name  that  matched.  This saves searching to find which numbered
-        subpattern it was. If you make a reference to a non-unique  named  sub-
+        subpattern it was.
-        pattern  from elsewhere in the pattern, the one that corresponds to the
-        lowest number is used. For further details of the interfaces  for  han-
+        If you make a backreference to a non-unique named subpattern from else-
-        dling named subpatterns, see the pcreapi documentation.
+        where  in the pattern, the one that corresponds to the first occurrence
+        of the name is used. In the absence of duplicate numbers (see the  pre-
+        vious  section)  this  is  the one with the lowest number. If you use a
+        named reference in a condition test (see the section  about  conditions
+        below),  either  to check whether a subpattern has matched, or to check
+        for recursion, all subpatterns with the same name are  tested.  If  the
+        condition  is  true for any one of them, the overall condition is true.
+        This is the same behaviour as testing by number. For further details of
+        the interfaces for handling named subpatterns, see the pcreapi documen-
+        tation.
+        Warning: You cannot use different names to distinguish between two sub-
+        patterns  with  the same number because PCRE uses only the numbers when
+        matching. For this reason, an error is given at compile time if differ-
+        ent  names  are given to subpatterns with the same number. However, you
+        can give the same name to subpatterns with the same number,  even  when
+        PCRE_DUPNAMES is not set.
  REPETITION
-Line 3917 
 REPETITION
+Line 4155 
 REPETITION
           a character class
           a back reference (see next section)
           a parenthesized subpattern (unless it is an assertion)
+          a recursive or "subroutine" call to a subpattern
         The general repetition quantifier specifies a minimum and maximum  num-
         ber  of  permitted matches, by giving the two numbers in curly brackets
-Line 3942 
 REPETITION
+Line 4181 
 REPETITION
         the  syntax of a quantifier, is taken as a literal character. For exam-
         ple, {,6} is not a quantifier, but a literal string of four characters.
-        In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to
+        In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to
         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-
         acters, each of which is represented by a two-byte sequence. Similarly,
         when Unicode property support is available, \X{3} matches three Unicode
-        extended  sequences,  each of which may be several bytes long (and they
+        extended sequences, each of which may be several bytes long  (and  they
         may be of different lengths).
         The quantifier {0} is permitted, causing the expression to behave as if
-        the previous item and the quantifier were not present.
+        the previous item and the quantifier were not present. This may be use-
+        ful  for  subpatterns that are referenced as subroutines from elsewhere
+        in the pattern. Items other than subpatterns that have a {0} quantifier
+        are omitted from the compiled pattern.
         For  convenience, the three most common quantifiers have single-charac-
         ter abbreviations:
-Line 4080 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 4322 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
           (?>\d+)foo
-        This  kind  of  parenthesis "locks up" the  part of the pattern it con-
+        This kind of parenthesis "locks up" the  part of the  pattern  it  con-
-        tains once it has matched, and a failure further into  the  pattern  is
+        tains  once  it  has matched, and a failure further into the pattern is
-        prevented  from  backtracking into it. Backtracking past it to previous
+        prevented from backtracking into it. Backtracking past it  to  previous
         items, however, works as normal.
-        An alternative description is that a subpattern of  this  type  matches
+        An  alternative  description  is that a subpattern of this type matches
-        the  string  of  characters  that an identical standalone pattern would
+        the string of characters that an  identical  standalone  pattern  would
         match, if anchored at the current point in the subject string.
         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
         such as the above example can be thought of as a maximizing repeat that
-        must swallow everything it can. So, while both \d+ and  \d+?  are  pre-
+        must  swallow  everything  it can. So, while both \d+ and \d+? are pre-
-        pared  to  adjust  the number of digits they match in order to make the
+        pared to adjust the number of digits they match in order  to  make  the
         rest of the pattern match, (?>\d+) can only match an entire sequence of
         digits.
-        Atomic  groups in general can of course contain arbitrarily complicated
+        Atomic groups in general can of course contain arbitrarily  complicated
-        subpatterns, and can be nested. However, when  the  subpattern  for  an
+        subpatterns,  and  can  be  nested. However, when the subpattern for an
         atomic group is just a single repeated item, as in the example above, a
-        simpler notation, called a "possessive quantifier" can  be  used.  This
+        simpler  notation,  called  a "possessive quantifier" can be used. This
-        consists  of  an  additional  + character following a quantifier. Using
+        consists of an additional + character  following  a  quantifier.  Using
         this notation, the previous example can be rewritten as
           \d++foo
-Line 4110 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 4352 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
           (abc|xyz){2,3}+
-        Possessive   quantifiers   are   always  greedy;  the  setting  of  the
+        Possessive  quantifiers  are  always  greedy;  the   setting   of   the
         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
-        simpler  forms  of atomic group. However, there is no difference in the
+        simpler forms of atomic group. However, there is no difference  in  the
-        meaning of a possessive quantifier and  the  equivalent  atomic  group,
+        meaning  of  a  possessive  quantifier and the equivalent atomic group,
-        though  there  may  be a performance difference; possessive quantifiers
+        though there may be a performance  difference;  possessive  quantifiers
         should be slightly faster.
-        The possessive quantifier syntax is an extension to the Perl  5.8  syn-
+        The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-
-        tax.   Jeffrey  Friedl  originated the idea (and the name) in the first
+        tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first
         edition of his book. Mike McCloskey liked it, so implemented it when he
-        built  Sun's Java package, and PCRE copied it from there. It ultimately
+        built Sun's Java package, and PCRE copied it from there. It  ultimately
         found its way into Perl at release 5.10.
         PCRE has an optimization that automatically "possessifies" certain sim-
-        ple  pattern  constructs.  For  example, the sequence A+B is treated as
+        ple pattern constructs. For example, the sequence  A+B  is  treated  as
-        A++B because there is no point in backtracking into a sequence  of  A's
+        A++B  because  there is no point in backtracking into a sequence of A's
         when B must follow.
-        When  a  pattern  contains an unlimited repeat inside a subpattern that
+        When a pattern contains an unlimited repeat inside  a  subpattern  that
-        can itself be repeated an unlimited number of  times,  the  use  of  an
+        can  itself  be  repeated  an  unlimited number of times, the use of an
-        atomic  group  is  the  only way to avoid some failing matches taking a
+        atomic group is the only way to avoid some  failing  matches  taking  a
         very long time indeed. The pattern
           (\D+|<\d+>)*[!?]
-        matches an unlimited number of substrings that either consist  of  non-
+        matches  an  unlimited number of substrings that either consist of non-
-        digits,  or  digits  enclosed in <>, followed by either ! or ?. When it
+        digits, or digits enclosed in <>, followed by either ! or  ?.  When  it
         matches, it runs quickly. However, if it is applied to
           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-        it takes a long time before reporting  failure.  This  is  because  the
+        it  takes  a  long  time  before reporting failure. This is because the
-        string  can be divided between the internal \D+ repeat and the external
+        string can be divided between the internal \D+ repeat and the  external
-        * repeat in a large number of ways, and all  have  to  be  tried.  (The
+        *  repeat  in  a  large  number of ways, and all have to be tried. (The
-        example  uses  [!?]  rather than a single character at the end, because
+        example uses [!?] rather than a single character at  the  end,  because
-        both PCRE and Perl have an optimization that allows  for  fast  failure
+        both  PCRE  and  Perl have an optimization that allows for fast failure
-        when  a single character is used. They remember the last single charac-
+        when a single character is used. They remember the last single  charac-
-        ter that is required for a match, and fail early if it is  not  present
+        ter  that  is required for a match, and fail early if it is not present
-        in  the  string.)  If  the pattern is changed so that it uses an atomic
+        in the string.) If the pattern is changed so that  it  uses  an  atomic
         group, like this:
           ((?>\D+)|<\d+>)*[!?]
-        sequences of non-digits cannot be broken, and failure happens  quickly.
+        sequences of non-digits cannot be broken, and failure happens quickly.
  BACK REFERENCES
-Line 4237 
 BACK REFERENCES
+Line 4479 
 BACK REFERENCES
         There  may be more than one back reference to the same subpattern. If a
         subpattern has not actually been used in a particular match,  any  back
-        references to it always fail. For example, the pattern
+        references to it always fail by default. For example, the pattern
           (a|(bc))\2
-        always  fails if it starts to match "a" rather than "bc". Because there
+        always  fails  if  it starts to match "a" rather than "bc". However, if
-        may be many capturing parentheses in a pattern,  all  digits  following
+        the PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back refer-
-        the  backslash  are taken as part of a potential back reference number.
+        ence to an unset value matches an empty string.
-        If the pattern continues with a digit character, some delimiter must be
-        used  to  terminate  the back reference. If the PCRE_EXTENDED option is
+        Because  there may be many capturing parentheses in a pattern, all dig-
-        set, this can be whitespace.  Otherwise an  empty  comment  (see  "Com-
+        its following a backslash are taken as part of a potential back  refer-
-        ments" below) can be used.
+        ence  number.   If  the  pattern continues with a digit character, some
+        delimiter must  be  used  to  terminate  the  back  reference.  If  the
-        A  back reference that occurs inside the parentheses to which it refers
+        PCRE_EXTENDED option is set, this can be whitespace. Otherwise, the \g{
-        fails when the subpattern is first used, so, for example,  (a\1)  never
+        syntax or an empty comment (see "Comments" below) can be used.
-        matches.   However,  such references can be useful inside repeated sub-
+        A back reference that occurs inside the parentheses to which it  refers
+        fails  when  the subpattern is first used, so, for example, (a\1) never
+        matches.  However, such references can be useful inside  repeated  sub-
         patterns. For example, the pattern
           (a|b\1)+
         matches any number of "a"s and also "aba", "ababbaa" etc. At each iter-
-        ation  of  the  subpattern,  the  back  reference matches the character
+        ation of the subpattern,  the  back  reference  matches  the  character
-        string corresponding to the previous iteration. In order  for  this  to
+        string  corresponding  to  the previous iteration. In order for this to
-        work,  the  pattern must be such that the first iteration does not need
+        work, the pattern must be such that the first iteration does  not  need
-        to match the back reference. This can be done using alternation, as  in
+        to  match the back reference. This can be done using alternation, as in
         the example above, or by a quantifier with a minimum of zero.
  ASSERTIONS
-        An  assertion  is  a  test on the characters following or preceding the
+        An assertion is a test on the characters  following  or  preceding  the
-        current matching point that does not actually consume  any  characters.
+        current  matching  point that does not actually consume any characters.
-        The  simple  assertions  coded  as  \b, \B, \A, \G, \Z, \z, ^ and $ are
+        The simple assertions coded as \b, \B, \A, \G, \Z,  \z,  ^  and  $  are
         described above.
-        More complicated assertions are coded as  subpatterns.  There  are  two
+        More  complicated  assertions  are  coded as subpatterns. There are two
-        kinds:  those  that  look  ahead of the current position in the subject
+        kinds: those that look ahead of the current  position  in  the  subject
-        string, and those that look  behind  it.  An  assertion  subpattern  is
+        string,  and  those  that  look  behind  it. An assertion subpattern is
-        matched  in  the  normal way, except that it does not cause the current
+        matched in the normal way, except that it does not  cause  the  current
         matching position to be changed.
-        Assertion subpatterns are not capturing subpatterns,  and  may  not  be
+        Assertion  subpatterns  are  not  capturing subpatterns, and may not be
-        repeated,  because  it  makes no sense to assert the same thing several
+        repeated, because it makes no sense to assert the  same  thing  several
-        times. If any kind of assertion contains capturing  subpatterns  within
+        times.  If  any kind of assertion contains capturing subpatterns within
-        it,  these are counted for the purposes of numbering the capturing sub-
+        it, these are counted for the purposes of numbering the capturing  sub-
         patterns in the whole pattern.  However, substring capturing is carried
-        out  only  for  positive assertions, because it does not make sense for
+        out only for positive assertions, because it does not  make  sense  for
         negative assertions.
     Lookahead assertions
-Line 4292 
 ASSERTIONS
+Line 4537 
 ASSERTIONS
           \w+(?=;)
-        matches  a word followed by a semicolon, but does not include the semi-
+        matches a word followed by a semicolon, but does not include the  semi-
         colon in the match, and
           foo(?!bar)
-        matches any occurrence of "foo" that is not  followed  by  "bar".  Note
+        matches  any  occurrence  of  "foo" that is not followed by "bar". Note
         that the apparently similar pattern
           (?!foo)bar
-        does  not  find  an  occurrence  of "bar" that is preceded by something
+        does not find an occurrence of "bar"  that  is  preceded  by  something
-        other than "foo"; it finds any occurrence of "bar" whatsoever,  because
+        other  than "foo"; it finds any occurrence of "bar" whatsoever, because
         the assertion (?!foo) is always true when the next three characters are
         "bar". A lookbehind assertion is needed to achieve the other effect.
         If you want to force a matching failure at some point in a pattern, the
-        most  convenient  way  to  do  it  is with (?!) because an empty string
+        most convenient way to do it is  with  (?!)  because  an  empty  string
-        always matches, so an assertion that requires there not to be an  empty
+        always  matches, so an assertion that requires there not to be an empty
-        string must always fail.
+        string must always fail.   The  Perl  5.10  backtracking  control  verb
+        (*FAIL) or (*F) is essentially a synonym for (?!).
     Lookbehind assertions
-Line 4333 
 ASSERTIONS
+Line 4579 
 ASSERTIONS
         causes an error at compile time. Branches that match  different  length
         strings  are permitted only at the top level of a lookbehind assertion.
-        This is an extension compared with  Perl  (at  least  for  5.8),  which
+        This is an extension compared with Perl (5.8 and 5.10), which  requires
-        requires  all branches to match the same length of string. An assertion
+        all branches to match the same length of string. An assertion such as
-        such as
           (?<=ab(c|de))
-        is not permitted, because its single top-level  branch  can  match  two
+        is  not  permitted,  because  its single top-level branch can match two
-        different  lengths,  but  it is acceptable if rewritten to use two top-
+        different lengths, but it is acceptable to PCRE if rewritten to use two
-        level branches:
+        top-level branches:
           (?<=abc|abde)
         In some cases, the Perl 5.10 escape sequence \K (see above) can be used
-        instead  of  a lookbehind assertion; this is not restricted to a fixed-
+        instead of  a  lookbehind  assertion  to  get  round  the  fixed-length
-        length.
+        restriction.
-        The implementation of lookbehind assertions is, for  each  alternative,
+        The  implementation  of lookbehind assertions is, for each alternative,
-        to  temporarily  move the current position back by the fixed length and
+        to temporarily move the current position back by the fixed  length  and
         then try to match. If there are insufficient characters before the cur-
         rent position, the assertion fails.
         PCRE does not allow the \C escape (which matches a single byte in UTF-8
-        mode) to appear in lookbehind assertions, because it makes it  impossi-
+        mode)  to appear in lookbehind assertions, because it makes it impossi-
-        ble  to  calculate the length of the lookbehind. The \X and \R escapes,
+        ble to calculate the length of the lookbehind. The \X and  \R  escapes,
         which can match different numbers of bytes, are also not permitted.
-        Possessive quantifiers can  be  used  in  conjunction  with  lookbehind
+        "Subroutine"  calls  (see below) such as (?2) or (?&X) are permitted in
-        assertions  to  specify  efficient  matching  at the end of the subject
+        lookbehinds, as long as the subpattern matches a  fixed-length  string.
-        string. Consider a simple pattern such as
+        Recursion, however, is not supported.
+        Possessive  quantifiers  can  be  used  in  conjunction with lookbehind
+        assertions to specify efficient matching of fixed-length strings at the
+        end of subject strings. Consider a simple pattern such as
           abcd$
-        when applied to a long string that does  not  match.  Because  matching
+        when  applied  to  a  long string that does not match. Because matching
         proceeds from left to right, PCRE will look for each "a" in the subject
-        and then see if what follows matches the rest of the  pattern.  If  the
+        and  then  see  if what follows matches the rest of the pattern. If the
         pattern is specified as
           ^.*abcd$
-        the  initial .* matches the entire string at first, but when this fails
+        the initial .* matches the entire string at first, but when this  fails
         (because there is no following "a"), it backtracks to match all but the
-        last  character,  then all but the last two characters, and so on. Once
+        last character, then all but the last two characters, and so  on.  Once
-        again the search for "a" covers the entire string, from right to  left,
+        again  the search for "a" covers the entire string, from right to left,
         so we are no better off. However, if the pattern is written as
           ^.*+(?<=abcd)
-        there  can  be  no backtracking for the .*+ item; it can match only the
+        there can be no backtracking for the .*+ item; it can  match  only  the
-        entire string. The subsequent lookbehind assertion does a  single  test
+        entire  string.  The subsequent lookbehind assertion does a single test
-        on  the last four characters. If it fails, the match fails immediately.
+        on the last four characters. If it fails, the match fails  immediately.
-        For long strings, this approach makes a significant difference  to  the
+        For  long  strings, this approach makes a significant difference to the
         processing time.
     Using multiple assertions
-Line 4392 
 ASSERTIONS
+Line 4641 
 ASSERTIONS
           (?<=\d{3})(?<!999)foo
-        matches  "foo" preceded by three digits that are not "999". Notice that
+        matches "foo" preceded by three digits that are not "999". Notice  that
-        each of the assertions is applied independently at the  same  point  in
+        each  of  the  assertions is applied independently at the same point in
-        the  subject  string.  First  there  is a check that the previous three
+        the subject string. First there is a  check  that  the  previous  three
-        characters are all digits, and then there is  a  check  that  the  same
+        characters  are  all  digits,  and  then there is a check that the same
         three characters are not "999".  This pattern does not match "foo" pre-
-        ceded by six characters, the first of which are  digits  and  the  last
+        ceded  by  six  characters,  the first of which are digits and the last
-        three  of  which  are not "999". For example, it doesn't match "123abc-
+        three of which are not "999". For example, it  doesn't  match  "123abc-
         foo". A pattern to do that is
           (?<=\d{3}...)(?<!999)foo
-        This time the first assertion looks at the  preceding  six  characters,
+        This  time  the  first assertion looks at the preceding six characters,
         checking that the first three are digits, and then the second assertion
         checks that the preceding three characters are not "999".
-Line 4411 
 ASSERTIONS
+Line 4660 
 ASSERTIONS
           (?<=(?<!foo)bar)baz
-        matches an occurrence of "baz" that is preceded by "bar" which in  turn
+        matches  an occurrence of "baz" that is preceded by "bar" which in turn
         is not preceded by "foo", while
           (?<=\d{3}(?!999)...)foo
-        is  another pattern that matches "foo" preceded by three digits and any
+        is another pattern that matches "foo" preceded by three digits and  any
         three characters that are not "999".
  CONDITIONAL SUBPATTERNS
-        It is possible to cause the matching process to obey a subpattern  con-
+        It  is possible to cause the matching process to obey a subpattern con-
-        ditionally  or to choose between two alternative subpatterns, depending
+        ditionally or to choose between two alternative subpatterns,  depending
-        on the result of an assertion, or whether a previous capturing  subpat-
+        on  the result of an assertion, or whether a specific capturing subpat-
-        tern  matched  or not. The two possible forms of conditional subpattern
+        tern has already been matched. The two possible  forms  of  conditional
-        are
+        subpattern are:
           (?(condition)yes-pattern)
           (?(condition)yes-pattern|no-pattern)
-        If the condition is satisfied, the yes-pattern is used;  otherwise  the
+        If  the  condition is satisfied, the yes-pattern is used; otherwise the
-        no-pattern  (if  present)  is used. If there are more than two alterna-
+        no-pattern (if present) is used. If there are more  than  two  alterna-
         tives in the subpattern, a compile-time error occurs.
-        There are four kinds of condition: references  to  subpatterns,  refer-
+        There  are  four  kinds of condition: references to subpatterns, refer-
         ences to recursion, a pseudo-condition called DEFINE, and assertions.
     Checking for a used subpattern by number
-        If  the  text between the parentheses consists of a sequence of digits,
+        If the text between the parentheses consists of a sequence  of  digits,
-        the condition is true if the capturing subpattern of  that  number  has
+        the condition is true if a capturing subpattern of that number has pre-
-        previously  matched.  An  alternative notation is to precede the digits
+        viously matched. If there is more than one  capturing  subpattern  with
-        with a plus or minus sign. In this case, the subpattern number is rela-
+        the  same  number  (see  the earlier section about duplicate subpattern
-        tive rather than absolute.  The most recently opened parentheses can be
+        numbers), the condition is true if any of them have been set. An alter-
-        referenced by (?(-1), the next most recent by (?(-2),  and  so  on.  In
+        native  notation is to precede the digits with a plus or minus sign. In
-        looping constructs it can also make sense to refer to subsequent groups
+        this case, the subpattern number is relative rather than absolute.  The
-        with constructs such as (?(+2).
+        most  recently opened parentheses can be referenced by (?(-1), the next
+        most recent by (?(-2), and so on. In looping  constructs  it  can  also
+        make  sense  to  refer  to  subsequent  groups  with constructs such as
+        (?(+2).
         Consider the following pattern, which  contains  non-significant  white
         space to make it more readable (assume the PCRE_EXTENDED option) and to
-Line 4490 
 CONDITIONAL SUBPATTERNS
+Line 4742 
 CONDITIONAL SUBPATTERNS
           (?<OPEN> \( )?    [^()]+    (?(<OPEN>) \) )
+        If  the  name used in a condition of this kind is a duplicate, the test
+        is applied to all subpatterns of the same name, and is true if any  one
+        of them has matched.
     Checking for pattern recursion
-Line 4500 
 CONDITIONAL SUBPATTERNS
+Line 4755 
 CONDITIONAL SUBPATTERNS
           (?(R3)...) or (?(R&name)...)
-        the condition is true if the most recent recursion is into the  subpat-
+        the condition is true if the most recent recursion is into a subpattern
-        tern  whose  number or name is given. This condition does not check the
+        whose number or name is given. This condition does not check the entire
-        entire recursion stack.
+        recursion stack. If the name used in a condition  of  this  kind  is  a
+        duplicate, the test is applied to all subpatterns of the same name, and
+        is true if any one of them is the most recent recursion.
-        At "top level", all these recursion test conditions are  false.  Recur-
+        At "top level", all these recursion test  conditions  are  false.   The
-        sive patterns are described below.
+        syntax for recursive patterns is described below.
     Defining subpatterns for use by reference only
-Line 4525 
 CONDITIONAL SUBPATTERNS
+Line 4782 
 CONDITIONAL SUBPATTERNS
         group  named "byte" is defined. This matches an individual component of
         an IPv4 address (a number less than 256). When  matching  takes  place,
         this  part  of  the pattern is skipped because DEFINE acts like a false
-        condition.
+        condition. The rest of the pattern uses references to the  named  group
+        to  match the four dot-separated components of an IPv4 address, insist-
-        The rest of the pattern uses references to the named group to match the
+        ing on a word boundary at each end.
-        four  dot-separated  components of an IPv4 address, insisting on a word
-        boundary at each end.
     Assertion conditions
-Line 4584 
 RECURSIVE PATTERNS
+Line 4839 
 RECURSIVE PATTERNS
         Obviously, PCRE cannot support the interpolation of Perl code. Instead,
         it supports special syntax for recursion of  the  entire  pattern,  and
         also  for  individual  subpattern  recursion. After its introduction in
-        PCRE and Python, this kind of recursion was  introduced  into  Perl  at
+        PCRE and Python, this kind of  recursion  was  subsequently  introduced
-        release 5.10.
+        into Perl at release 5.10.
         A  special  item  that consists of (? followed by a number greater than
         zero and a closing parenthesis is a recursive call of the subpattern of
-Line 4594 
 RECURSIVE PATTERNS
+Line 4849 
 RECURSIVE PATTERNS
         tion.)  The special item (?R) or (?0) is a recursive call of the entire
         regular expression.
-        In PCRE (like Python, but unlike Perl), a recursive subpattern call  is
+        This PCRE pattern solves the nested  parentheses  problem  (assume  the
-        always treated as an atomic group. That is, once it has matched some of
-        the subject string, it is never re-entered, even if it contains untried
-        alternatives and there is a subsequent matching failure.
-        This  PCRE  pattern  solves  the nested parentheses problem (assume the
         PCRE_EXTENDED option is set so that white space is ignored):
-          \( ( (?>[^()]+) | (?R) )* \)
+          \( ( [^()]++ | (?R) )* \)
-        First it matches an opening parenthesis. Then it matches any number  of
+        First  it matches an opening parenthesis. Then it matches any number of
-        substrings  which  can  either  be  a sequence of non-parentheses, or a
+        substrings which can either be a  sequence  of  non-parentheses,  or  a
-        recursive match of the pattern itself (that is, a  correctly  parenthe-
+        recursive  match  of the pattern itself (that is, a correctly parenthe-
-        sized substring).  Finally there is a closing parenthesis.
+        sized substring).  Finally there is a closing parenthesis. Note the use
+        of a possessive quantifier to avoid backtracking into sequences of non-
+        parentheses.
-        If  this  were  part of a larger pattern, you would not want to recurse
+        If this were part of a larger pattern, you would not  want  to  recurse
         the entire pattern, so instead you could use this:
-          ( \( ( (?>[^()]+) | (?1) )* \) )
+          ( \( ( [^()]++ | (?1) )* \) )
-        We have put the pattern into parentheses, and caused the  recursion  to
+        We  have  put the pattern into parentheses, and caused the recursion to
         refer to them instead of the whole pattern.
-        In  a  larger  pattern,  keeping  track  of  parenthesis numbers can be
+        In a larger pattern,  keeping  track  of  parenthesis  numbers  can  be
-        tricky. This is made easier by the use of relative references. (A  Perl
+        tricky.  This  is made easier by the use of relative references (a Perl
-.10  feature.)   Instead  of  (?1)  in the pattern above you can write
+.10 feature).  Instead of (?1) in the  pattern  above  you  can  write
         (?-2) to refer to the second most recently opened parentheses preceding
-        the  recursion.  In  other  words,  a  negative number counts capturing
+        the recursion. In other  words,  a  negative  number  counts  capturing
         parentheses leftwards from the point at which it is encountered.
-        It is also possible to refer to  subsequently  opened  parentheses,  by
+        It  is  also  possible  to refer to subsequently opened parentheses, by
-        writing  references  such  as (?+2). However, these cannot be recursive
+        writing references such as (?+2). However, these  cannot  be  recursive
-        because the reference is not inside the  parentheses  that  are  refer-
+        because  the  reference  is  not inside the parentheses that are refer-
-        enced.  They  are  always  "subroutine" calls, as described in the next
+        enced. They are always "subroutine" calls, as  described  in  the  next
         section.
-        An alternative approach is to use named parentheses instead.  The  Perl
+        An  alternative  approach is to use named parentheses instead. The Perl
-        syntax  for  this  is (?&name); PCRE's earlier syntax (?P>name) is also
+        syntax for this is (?&name); PCRE's earlier syntax  (?P>name)  is  also
         supported. We could rewrite the above example as follows:
-          (?<pn> \( ( (?>[^()]+) | (?&pn) )* \) )
+          (?<pn> \( ( [^()]++ | (?&pn) )* \) )
-        If there is more than one subpattern with the same name,  the  earliest
+        If  there  is more than one subpattern with the same name, the earliest
         one is used.
-        This  particular  example pattern that we have been looking at contains
+        This particular example pattern that we have been looking  at  contains
-        nested unlimited repeats, and so the use of atomic grouping for  match-
+        nested unlimited repeats, and so the use of a possessive quantifier for
-        ing  strings  of non-parentheses is important when applying the pattern
+        matching strings of non-parentheses is important when applying the pat-
-        to strings that do not match. For example, when this pattern is applied
+        tern  to  strings  that do not match. For example, when this pattern is
-        to
+        applied to
           (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa()
-        it  yields "no match" quickly. However, if atomic grouping is not used,
+        it yields "no match" quickly. However, if a  possessive  quantifier  is
-        the match runs for a very long time indeed because there  are  so  many
+        not  used, the match runs for a very long time indeed because there are
-        different  ways  the  + and * repeats can carve up the subject, and all
+        so many different ways the + and * repeats can carve  up  the  subject,
-        have to be tested before failure can be reported.
+        and all have to be tested before failure can be reported.
-        At the end of a match, the values set for any capturing subpatterns are
+        At  the  end  of a match, the values of capturing parentheses are those
-        those from the outermost level of the recursion at which the subpattern
+        from the outermost level. If you want to obtain intermediate values,  a
-        value is set.  If you want to obtain  intermediate  values,  a  callout
+        callout  function can be used (see below and the pcrecallout documenta-
-        function  can be used (see below and the pcrecallout documentation). If
+        tion). If the pattern above is matched against
-        the pattern above is matched against
           (ab(cd)ef)
-        the value for the capturing parentheses is  "ef",  which  is  the  last
+        the value for the inner capturing parentheses  (numbered  2)  is  "ef",
-        value  taken  on at the top level. If additional parentheses are added,
+        which  is the last value taken on at the top level. If a capturing sub-
-        giving
+        pattern is not matched at the top level, its final value is unset, even
+        if it is (temporarily) set at a deeper level.
-          \( ( ( (?>[^()]+) | (?R) )* ) \)
-             ^                        ^
+        If  there are more than 15 capturing parentheses in a pattern, PCRE has
-             ^                        ^
+        to obtain extra memory to store data during a recursion, which it  does
+        by using pcre_malloc, freeing it via pcre_free afterwards. If no memory
-        the string they capture is "ab(cd)ef", the contents of  the  top  level
+        can be obtained, the match fails with the PCRE_ERROR_NOMEMORY error.
-        parentheses.  If there are more than 15 capturing parentheses in a pat-
-        tern, PCRE has to obtain extra memory to store data during a recursion,
+        Do not confuse the (?R) item with the condition (R),  which  tests  for
-        which  it  does  by  using pcre_malloc, freeing it via pcre_free after-
+        recursion.   Consider  this pattern, which matches text in angle brack-
-        wards. If  no  memory  can  be  obtained,  the  match  fails  with  the
+        ets, allowing for arbitrary nesting. Only digits are allowed in  nested
-        PCRE_ERROR_NOMEMORY error.
+        brackets  (that is, when recursing), whereas any characters are permit-
-        Do  not  confuse  the (?R) item with the condition (R), which tests for
-        recursion.  Consider this pattern, which matches text in  angle  brack-
-        ets,  allowing for arbitrary nesting. Only digits are allowed in nested
-        brackets (that is, when recursing), whereas any characters are  permit-
         ted at the outer level.
           < (?: (?(R) \d++  | [^<>]*+) | (?R)) * >
-        In  this  pattern, (?(R) is the start of a conditional subpattern, with
+        In this pattern, (?(R) is the start of a conditional  subpattern,  with
-        two different alternatives for the recursive and  non-recursive  cases.
+        two  different  alternatives for the recursive and non-recursive cases.
         The (?R) item is the actual recursive call.
+    Recursion difference from Perl
+        In PCRE (like Python, but unlike Perl), a recursive subpattern call  is
+        always treated as an atomic group. That is, once it has matched some of
+        the subject string, it is never re-entered, even if it contains untried
+        alternatives  and  there  is a subsequent matching failure. This can be
+        illustrated by the following pattern, which purports to match a  palin-
+        dromic  string  that contains an odd number of characters (for example,
+        "a", "aba", "abcba", "abcdcba"):
+          ^(.|(.)(?1)\2)$
+        The idea is that it either matches a single character, or two identical
+        characters  surrounding  a sub-palindrome. In Perl, this pattern works;
+        in PCRE it does not if the pattern is  longer  than  three  characters.
+        Consider the subject string "abcba":
+        At  the  top level, the first character is matched, but as it is not at
+        the end of the string, the first alternative fails; the second alterna-
+        tive is taken and the recursion kicks in. The recursive call to subpat-
+        tern 1 successfully matches the next character ("b").  (Note  that  the
+        beginning and end of line tests are not part of the recursion).
+        Back  at  the top level, the next character ("c") is compared with what
+        subpattern 2 matched, which was "a". This fails. Because the  recursion
+        is  treated  as  an atomic group, there are now no backtracking points,
+        and so the entire match fails. (Perl is able, at  this  point,  to  re-
+        enter  the  recursion  and try the second alternative.) However, if the
+        pattern is written with the alternatives in the other order, things are
+        different:
+          ^((.)(?1)\2|.)$
+        This  time,  the recursing alternative is tried first, and continues to
+        recurse until it runs out of characters, at which point  the  recursion
+        fails.  But  this  time  we  do  have another alternative to try at the
+        higher level. That is the big difference:  in  the  previous  case  the
+        remaining alternative is at a deeper recursion level, which PCRE cannot
+        use.
+        To change the pattern so that matches all palindromic strings, not just
+        those  with  an  odd number of characters, it is tempting to change the
+        pattern to this:
+          ^((.)(?1)\2|.?)$
+        Again, this works in Perl, but not in PCRE, and for  the  same  reason.
+        When  a  deeper  recursion has matched a single character, it cannot be
+        entered again in order to match an empty string.  The  solution  is  to
+        separate  the two cases, and write out the odd and even cases as alter-
+        natives at the higher level:
+          ^(?:((.)(?1)\2|)|((.)(?3)\4|.))
+        If you want to match typical palindromic phrases, the  pattern  has  to
+        ignore all non-word characters, which can be done like this:
+          ^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$
+        If run with the PCRE_CASELESS option, this pattern matches phrases such
+        as "A man, a plan, a canal: Panama!" and it works well in both PCRE and
+        Perl.  Note the use of the possessive quantifier *+ to avoid backtrack-
+        ing into sequences of non-word characters. Without this, PCRE  takes  a
+        great  deal  longer  (ten  times or more) to match typical phrases, and
+        Perl takes so long that you think it has gone into a loop.
+        WARNING: The palindrome-matching patterns above work only if  the  sub-
+        ject  string  does not start with a palindrome that is shorter than the
+        entire string.  For example, although "abcba" is correctly matched,  if
+        the  subject  is "ababa", PCRE finds the palindrome "aba" at the start,
+        then fails at top level because the end of the string does not  follow.
+        Once  again, it cannot jump back into the recursion to try other alter-
+        natives, so the entire match fails.
  SUBPATTERNS AS SUBROUTINES
         If the syntax for a recursive subpattern reference (either by number or
-        by name) is used outside the parentheses to which it refers,  it  oper-
+        by  name)  is used outside the parentheses to which it refers, it oper-
-        ates  like a subroutine in a programming language. The "called" subpat-
+        ates like a subroutine in a programming language. The "called"  subpat-
         tern may be defined before or after the reference. A numbered reference
         can be absolute or relative, as in these examples:
-Line 4704 
 SUBPATTERNS AS SUBROUTINES
+Line 5024 
 SUBPATTERNS AS SUBROUTINES
           (sens|respons)e and \1ibility
-        matches  "sense and sensibility" and "response and responsibility", but
+        matches "sense and sensibility" and "response and responsibility",  but
         not "sense and responsibility". If instead the pattern
           (sens|respons)e and (?1)ibility
-        is used, it does match "sense and responsibility" as well as the  other
+        is  used, it does match "sense and responsibility" as well as the other
-        two  strings.  Another  example  is  given  in the discussion of DEFINE
+        two strings. Another example is  given  in  the  discussion  of  DEFINE
         above.
-        Like recursive subpatterns, a "subroutine" call is always treated as an
+        Like  recursive  subpatterns, a subroutine call is always treated as an
-        atomic  group. That is, once it has matched some of the subject string,
+        atomic group. That is, once it has matched some of the subject  string,
-        it is never re-entered, even if it contains  untried  alternatives  and
+        it  is  never  re-entered, even if it contains untried alternatives and
-        there is a subsequent matching failure.
+        there is a subsequent matching failure. Any capturing parentheses  that
+        are  set  during  the  subroutine  call revert to their previous values
+        afterwards.
-        When  a  subpattern is used as a subroutine, processing options such as
+        Wh