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+ -----------------------------------------------------------------------------
+ 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
+ separate text files for the pcregrep and pcretest commands.
+ -----------------------------------------------------------------------------
+ PCRE(3)                                                                PCRE(3)
  NAME
-      pcre - Perl-compatible regular expressions.
+        PCRE - Perl-compatible regular expressions
+ 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.  The current implementation of PCRE (release
+.x) corresponds approximately with Perl  5.8,  including  support  for
+        UTF-8 encoded strings and Unicode general category properties. However,
+        this support has to be explicitly enabled; it is not the default.
+        PCRE is written in C and released as a C library. A  number  of  people
+        have  written  wrappers and interfaces of various kinds. A C++ class is
+        included in these contributions, which can  be  found  in  the  Contrib
+        directory at the primary FTP site, which is:
+        ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
+        Details  of  exactly which Perl regular expression features are and are
+        not supported by PCRE are given in separate documents. See the pcrepat-
+        tern and pcrecompat pages.
+        Some  features  of  PCRE can be included, excluded, or changed when the
+        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
+        in the source distribution.
+ 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
+        of searching. The sections are as follows:
+          pcre              this document
+          pcreapi           details of PCRE's native API
+          pcrebuild         options for building PCRE
+          pcrecallout       details of the callout feature
+          pcrecompat        discussion of Perl compatibility
+          pcregrep          description of the pcregrep command
+          pcrepartial       details of the partial matching facility
+          pcrepattern       syntax and semantics of supported
+                              regular expressions
+          pcreperform       discussion of performance issues
+          pcreposix         the POSIX-compatible API
+          pcreprecompile    details of saving and re-using precompiled patterns
+          pcresample        discussion of the sample program
+          pcretest          description of the pcretest testing command
+        In  addition,  in the "man" and HTML formats, there is a short page for
+        each library function, listing its arguments and results.
- SYNOPSIS
+ LIMITATIONS
-      #include <pcre.h>
+        There are some size limitations in PCRE but it is hoped that they  will
+        never in practice be relevant.
-      pcre *pcre_compile(const char *pattern, int options,
+        The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
-           const char **errptr, int *erroffset,
+        is compiled with the default internal linkage size of 2. If you want to
-           const unsigned char *tableptr);
+        process  regular  expressions  that are truly enormous, you can compile
+        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
+        the  source  distribution and the pcrebuild documentation for details).
+        In these cases the limit is substantially larger.  However,  the  speed
+        of execution will be slower.
+        All values in repeating quantifiers must be less than 65536.  The maxi-
+        mum number of capturing subpatterns is 65535.
+        There is no limit to the number of non-capturing subpatterns,  but  the
+        maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,
+        including capturing subpatterns, assertions, and other types of subpat-
+        tern, is 200.
+        The  maximum  length of a subject string is the largest positive number
+        that an integer variable can hold. However, PCRE uses recursion to han-
+        dle  subpatterns  and indefinite repetition. This means that the avail-
+        able stack space may limit the size of a subject  string  that  can  be
+        processed by certain patterns.
+ UTF-8 AND UNICODE PROPERTY SUPPORT
+        From  release  3.3,  PCRE  has  had  some support for character strings
+        encoded in the UTF-8 format. For release 4.0 this was greatly  extended
+        to  cover  most common requirements, and in release 5.0 additional sup-
+        port for Unicode general category properties was added.
+        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
+        any  subject  strings  that are matched against it are treated as UTF-8
+        strings instead of just strings of bytes.
+        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
+        is limited to testing the PCRE_UTF8 flag in several places,  so  should
+        not be very large.
+        If PCRE is built with Unicode character property support (which implies
+        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
+        for  a decimal number. A full list is given in the pcrepattern documen-
+        tation. The PCRE library is increased in size by about 90K when Unicode
+        property support is included.
+        The following comments apply when PCRE is running in UTF-8 mode:
+.  When you set the PCRE_UTF8 flag, the strings passed as patterns and
+        subjects are checked for validity on entry to the  relevant  functions.
+        If an invalid UTF-8 string is passed, an error return 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 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 to PCRE when
+        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may
+        crash.
+. In a pattern, the escape sequence \x{...}, where the contents of the
+        braces is a string of hexadecimal digits, is  interpreted  as  a  UTF-8
+        character  whose code number is the given hexadecimal number, for exam-
+        ple: \x{1234}. If a non-hexadecimal digit appears between  the  braces,
+        the item is not recognized.  This escape sequence can be used either as
+        a literal, or within a character class.
+. The original hexadecimal escape sequence, \xhh, matches  a  two-byte
+        UTF-8 character if the value is greater than 127.
+.  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-
+        gle byte.
+.  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.
+. 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-
+        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
+        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
+        \p{Nd}.
+.  Similarly,  characters that match the POSIX named character classes
+        are all low-valued characters.
+. Case-insensitive matching applies only to  characters  whose  values
+        are  less than 128, unless PCRE is built with Unicode property support.
+        Even when Unicode property support is available, PCRE  still  uses  its
+        own  character  tables when checking the case of low-valued characters,
+        so as not to degrade performance.  The Unicode property information  is
+        used only for characters with higher values.
-      pcre_extra *pcre_study(const pcre *code, int options,
-           const char **errptr);
-      int pcre_exec(const pcre *code, const pcre_extra *extra,
+ AUTHOR
-           const char *subject, int length, int startoffset,
-           int options, int *ovector, int ovecsize);
-      int pcre_copy_substring(const char *subject, int *ovector,
+        Philip Hazel <ph10@cam.ac.uk>
-           int stringcount, int stringnumber, char *buffer,
+        University Computing Service,
-           int buffersize);
+        Cambridge CB2 3QG, England.
+        Phone: +44 1223 334714
+ Last updated: 09 September 2004
+ Copyright (c) 1997-2004 University of Cambridge.
+ -----------------------------------------------------------------------------
-      int pcre_get_substring(const char *subject, int *ovector,
+ PCRE(3)                                                                PCRE(3)
-           int stringcount, int stringnumber,
-           const char **stringptr);
-      int pcre_get_substring_list(const char *subject,
-           int *ovector, int stringcount, const char ***listptr);
-      void pcre_free_substring(const char *stringptr);
-      void pcre_free_substring_list(const char **stringptr);
+ NAME
+        PCRE - Perl-compatible regular expressions
-      const unsigned char *pcre_maketables(void);
+ PCRE BUILD-TIME OPTIONS
-      int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
+        This  document  describes  the  optional  features  of PCRE that can be
-           int what, void *where);
+        selected when the library is compiled. They are all selected, or  dese-
+        lected, by providing options to the configure script that is run before
+        the make command. The complete list of  options  for  configure  (which
+        includes  the  standard  ones such as the selection of the installation
+        directory) can be obtained by running
+          ./configure --help
+        The following sections describe certain 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  works,
+        --enable  and  --disable  always  come  in  pairs, so the complementary
+        option always exists as well, but as it specifies the  default,  it  is
+        not described.
-      int pcre_info(const pcre *code, int *optptr, *firstcharptr);
-      char *pcre_version(void);
+ UTF-8 SUPPORT
-      void *(*pcre_malloc)(size_t);
+        To build PCRE with support for UTF-8 character strings, add
-      void (*pcre_free)(void *);
+          --enable-utf8
+        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
+        have  have to set the PCRE_UTF8 option when you call the pcre_compile()
+        function.
+ UNICODE CHARACTER PROPERTY SUPPORT
- DESCRIPTION
+        UTF-8 support allows PCRE to process character values greater than  255
-      The PCRE library is a set of functions that implement  regu-
+        in  the  strings that it handles. On its own, however, it does not pro-
-      lar  expression  pattern  matching using the same syntax and
+        vide any facilities for accessing the properties of such characters. If
-      semantics as Perl  5,  with  just  a  few  differences  (see
+        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
+        not explicitly requested it.
+        Including  Unicode  property  support  adds around 90K of tables to the
+        PCRE library, approximately doubling its size. Only the  general  cate-
+        gory  properties  such as Lu and Nd are supported. Details are given in
+        the pcrepattern documentation.
+ CODE VALUE OF NEWLINE
+        By default, PCRE treats character 10 (linefeed) as the newline  charac-
+        ter. This is the normal newline character on Unix-like systems. You can
+        compile PCRE to use character 13 (carriage return) instead by adding
+          --enable-newline-is-cr
+        to the configure command. For completeness there is  also  a  --enable-
+        newline-is-lf  option,  which explicitly specifies linefeed as the new-
+        line character.
+ BUILDING SHARED AND STATIC LIBRARIES
+        The PCRE building process uses libtool to build both shared and  static
+        Unix  libraries by default. You can suppress one of these by adding one
+        of
+          --disable-shared
+          --disable-static
+        to the configure command, as required.
+ POSIX MALLOC USAGE
+        When PCRE is called through the POSIX interface (see the pcreposix doc-
+        umentation),  additional  working  storage  is required for holding the
+        pointers to capturing substrings, because PCRE requires three  integers
+        per  substring,  whereas  the POSIX interface provides only two. If the
+        number of expected substrings is small, the wrapper function uses space
+        on the stack, because this is faster than using malloc() for each call.
+        The default threshold above which the stack is no longer used is 10; it
+        can be changed by adding a setting such as
+          --with-posix-malloc-threshold=20
+        to the configure command.
+ LIMITING PCRE RESOURCE USAGE
+        Internally,  PCRE has a function called match(), which it calls repeat-
+        edly (possibly recursively) when matching a pattern. By controlling the
+        maximum  number  of  times  this 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 limit can be changed at run time, as
+        described in the pcreapi documentation. The default is 10 million,  but
+        this can be changed by adding a setting such as
+          --with-match-limit=500000
+        to the configure command.
+ HANDLING VERY LARGE PATTERNS
+        Within  a  compiled  pattern,  offset values are used to point from one
+        part to another (for example, from an opening parenthesis to an  alter-
+        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
+        is  possible  to compile PCRE to use three-byte or four-byte offsets by
+        adding a setting such as
+          --with-link-size=3
+        to the configure command. The value given must be 2,  3,  or  4.  Using
+        longer  offsets slows down the operation of PCRE because it has to load
+        additional bytes when handling them.
+        If you build PCRE with an increased link size, test 2 (and  test  5  if
+        you  are using UTF-8) will fail. Part of the output of these tests is a
+        representation of the compiled pattern, and this changes with the  link
+        size.
+ AVOIDING EXCESSIVE STACK USAGE
+        PCRE  implements  backtracking while matching by making recursive calls
+        to an internal function called match(). In environments where the  size
+        of the stack is limited, this can severely limit PCRE's operation. (The
+        Unix environment does not usually suffer from this problem.) An  alter-
+        native  approach  that  uses  memory  from  the  heap to remember data,
+        instead of using recursive function calls, has been implemented to work
+        round  this  problem. If you want to build a version of PCRE that works
+        this way, add
+          --disable-stack-for-recursion
+        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. Separate functions are provided because  the  usage  is
+        very  predictable:  the  block sizes requested are always the same, and
+        the blocks are always freed in reverse order. A calling  program  might
+        be  able  to implement optimized functions that perform better than the
+        standard malloc() and  free()  functions.  PCRE  runs  noticeably  more
+        slowly when built in this way.
+ USING EBCDIC CODE
+        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).
+        PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by
+        adding
+          --enable-ebcdic
+        to the configure command.
+ Last updated: 09 September 2004
+ Copyright (c) 1997-2004 University of Cambridge.
+ -----------------------------------------------------------------------------
+ PCRE(3)                                                                PCRE(3)
+ NAME
+        PCRE - Perl-compatible regular expressions
+ PCRE NATIVE API
+        #include <pcre.h>
+        pcre *pcre_compile(const char *pattern, int options,
+             const char **errptr, int *erroffset,
+             const unsigned char *tableptr);
+        pcre_extra *pcre_study(const pcre *code, int options,
+             const char **errptr);
+        int pcre_exec(const pcre *code, const pcre_extra *extra,
+             const char *subject, int length, int startoffset,
+             int options, int *ovector, int ovecsize);
+        int pcre_copy_named_substring(const pcre *code,
+             const char *subject, int *ovector,
+             int stringcount, const char *stringname,
+             char *buffer, int buffersize);
+        int pcre_copy_substring(const char *subject, int *ovector,
+             int stringcount, int stringnumber, char *buffer,
+             int buffersize);
+        int pcre_get_named_substring(const pcre *code,
+             const char *subject, int *ovector,
+             int stringcount, const char *stringname,
+             const char **stringptr);
+        int pcre_get_stringnumber(const pcre *code,
+             const char *name);
+        int pcre_get_substring(const char *subject, int *ovector,
+             int stringcount, int stringnumber,
+             const char **stringptr);
+        int pcre_get_substring_list(const char *subject,
+             int *ovector, int stringcount, const char ***listptr);
+        void pcre_free_substring(const char *stringptr);
+        void pcre_free_substring_list(const char **stringptr);
+        const unsigned char *pcre_maketables(void);
+        int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
+             int what, void *where);
+        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
+        int pcre_config(int what, void *where);
+        char *pcre_version(void);
+        void *(*pcre_malloc)(size_t);
+        void (*pcre_free)(void *);
+        void *(*pcre_stack_malloc)(size_t);
+        void (*pcre_stack_free)(void *);
+        int (*pcre_callout)(pcre_callout_block *);
+ PCRE API OVERVIEW
+        PCRE has its own native API, which is described in this document. There
+        is also a set of wrapper functions that correspond to the POSIX regular
+        expression API.  These are described in the pcreposix documentation.
+        The  native  API  function  prototypes  are  defined in the header file
+        pcre.h, and on Unix systems the library itself is  called  libpcre.  It
+        can normally be accessed by adding -lpcre to the command for linking an
+        application  that  uses  PCRE.  The  header  file  defines  the  macros
+        PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
+        bers for the library.  Applications can use these  to  include  support
+        for different releases of PCRE.
+        The  functions  pcre_compile(),  pcre_study(), and pcre_exec() are used
+        for compiling and matching regular expressions. A sample  program  that
+        demonstrates  the  simplest  way  of using them is provided in the file
+        called pcredemo.c in the source distribution. The pcresample documenta-
+        tion describes how to run it.
+        In  addition  to  the  main compiling and matching functions, there are
+        convenience functions for extracting captured substrings from a matched
+        subject string.  They are:
+          pcre_copy_substring()
+          pcre_copy_named_substring()
+          pcre_get_substring()
+          pcre_get_named_substring()
+          pcre_get_substring_list()
+          pcre_get_stringnumber()
+        pcre_free_substring() and pcre_free_substring_list() are also provided,
+        to free the memory used for extracted strings.
+        The function pcre_maketables() is used to  build  a  set  of  character
+        tables   in  the  current  locale  for  passing  to  pcre_compile()  or
+        pcre_exec().  This is an optional facility that is  provided  for  spe-
+        cialist use. Most commonly, no special tables are passed, in which case
+        internal tables that are generated when PCRE is built are used.
+        The function pcre_fullinfo() is used to find out  information  about  a
+        compiled  pattern; pcre_info() is an obsolete version that returns only
+        some of the available information, but is retained for  backwards  com-
+        patibility.   The function pcre_version() returns a pointer to a string
+        containing the version of PCRE and its date of release.
+        The global variables pcre_malloc and pcre_free  initially  contain  the
+        entry  points  of  the  standard malloc() and free() functions, respec-
+        tively. PCRE calls the memory management functions via these variables,
+        so  a  calling  program  can replace them if it wishes to intercept the
+        calls. This should be done before calling any PCRE functions.
-      below).  The  current  implementation  corresponds  to  Perl
+        The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
-.005, with some additional features  from  later  versions.
+        indirections  to  memory  management functions. These special functions
-      This  includes  some  experimental,  incomplete  support for
+        are used only when PCRE is compiled to use  the  heap  for  remembering
-      UTF-8 encoded strings. Details of exactly what is  and  what
+        data,  instead  of recursive function calls. This is a non-standard way
-      is not supported are given below.
+        of building PCRE, for use in environments  that  have  limited  stacks.
+        Because  of  the greater use of memory management, it runs more slowly.
+        Separate functions are provided so that special-purpose  external  code
+        can be used for this case. When used, these functions are always called
+        in a stack-like manner (last obtained, first  freed),  and  always  for
+        memory blocks of the same size.
-      PCRE has its own native API,  which  is  described  in  this
+        The global variable pcre_callout initially contains NULL. It can be set
-      document.  There  is  also  a  set of wrapper functions that
+        by the caller to a "callout" function, which PCRE  will  then  call  at
-      correspond to the POSIX regular expression API.   These  are
+        specified  points during a matching operation. Details are given in the
-      described in the pcreposix documentation.
+        pcrecallout documentation.
-      The native API function prototypes are defined in the header
-      file  pcre.h,  and  on  Unix  systems  the library itself is
-      called libpcre.a, so can be accessed by adding -lpcre to the
-      command  for  linking  an  application  which  calls it. The
-      header file defines the macros PCRE_MAJOR and PCRE_MINOR  to
-      contain the major and minor release numbers for the library.
-      Applications can use these to include support for  different
-      releases.
-      The functions pcre_compile(), pcre_study(), and  pcre_exec()
+ MULTITHREADING
-      are used for compiling and matching regular expressions.
-      The functions  pcre_copy_substring(),  pcre_get_substring(),
+        The PCRE functions can be used in  multi-threading  applications,  with
-      and  pcre_get_substring_list() are convenience functions for
+        the  proviso  that  the  memory  management  functions  pointed  to  by
-      extracting  captured  substrings  from  a  matched   subject
+        pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
-      string; pcre_free_substring() and pcre_free_substring_list()
+        callout function pointed to by pcre_callout, are shared by all threads.
-      are also provided, to free the  memory  used  for  extracted
-      strings.
-      The function pcre_maketables() is used (optionally) to build
+        The compiled form of a regular expression is not altered during  match-
-      a  set of character tables in the current locale for passing
+        ing, so the same compiled pattern can safely be used by several threads
-      to pcre_compile().
+        at once.
-      The function pcre_fullinfo() is used to find out information
-      about a compiled pattern; pcre_info() is an obsolete version
-      which returns only some of the available information, but is
-      retained   for   backwards   compatibility.    The  function
-      pcre_version() returns a pointer to a string containing  the
-      version of PCRE and its date of release.
-      The global variables  pcre_malloc  and  pcre_free  initially
+ SAVING PRECOMPILED PATTERNS FOR LATER USE
-      contain the entry points of the standard malloc() and free()
-      functions respectively. PCRE  calls  the  memory  management
-      functions  via  these  variables,  so  a calling program can
-      replace them if it  wishes  to  intercept  the  calls.  This
-      should be done before calling any PCRE functions.
+        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
+        than the one on which  it  was  compiled.  Details  are  given  in  the
+        pcreprecompile documentation.
- MULTI-THREADING
+ CHECKING BUILD-TIME OPTIONS
-      The  PCRE  functions  can   be   used   in   multi-threading
+        int pcre_config(int what, void *where);
+        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-
+        tures.
+        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
+        available:
+          PCRE_CONFIG_UTF8
- SunOS 5.8                 Last change:                          2
+        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
+        character properties is available; otherwise it is set to zero.
-      applications,  with  the  proviso that the memory management
+          PCRE_CONFIG_NEWLINE
-      functions pointed to by pcre_malloc and pcre_free are shared
-      by all threads.
-      The compiled form of a regular  expression  is  not  altered
+        The  output  is an integer that is set to the value of the code that is
-      during  matching, so the same compiled pattern can safely be
+        used for the newline character. It is either linefeed (10) or  carriage
-      used by several threads at once.
+        return  (13),  and  should  normally be the standard character for your
+        operating system.
+          PCRE_CONFIG_LINK_SIZE
+        The output is an integer that contains the number  of  bytes  used  for
+        internal linkage in compiled regular expressions. The value is 2, 3, or
+. Larger values allow larger regular expressions to  be  compiled,  at
+        the  expense  of  slower matching. The default value of 2 is sufficient
+        for all but the most massive patterns, since  it  allows  the  compiled
+        pattern to be up to 64K in size.
+          PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
+        The  output  is  an integer that contains the threshold above which the
+        POSIX interface uses malloc() for output vectors. Further  details  are
+        given in the pcreposix documentation.
+          PCRE_CONFIG_MATCH_LIMIT
+        The output is an integer that gives the default limit for the number of
+        internal matching function calls in a  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 is
+        implemented by recursive function calls that use 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,  pcre_stack_malloc  and
+        pcre_stack_free are called to manage memory blocks on  the  heap,  thus
+        avoiding the use of the stack.
  COMPILING A PATTERN
-      The function pcre_compile() is called to compile  a  pattern
-      into  an internal form. The pattern is a C string terminated
-      by a binary zero, and is passed in the argument  pattern.  A
-      pointer  to  a  single  block of memory that is obtained via
-      pcre_malloc is returned. This contains the compiled code and
-      related data. The pcre type is defined for this for conveni-
-      ence, but in fact pcre is just a typedef for void, since the
-      contents  of  the block are not externally defined. It is up
-      to the caller to free  the  memory  when  it  is  no  longer
-      required.
-      The size of a compiled pattern is  roughly  proportional  to
-      the length of the pattern string, except that each character
-      class (other than those containing just a single  character,
-      negated  or  not)  requires 33 bytes, and repeat quantifiers
-      with a minimum greater than one or a bounded  maximum  cause
-      the  relevant  portions of the compiled pattern to be repli-
-      cated.
-      The options argument contains independent bits  that  affect
-      the  compilation.  It  should  be  zero  if  no  options are
-      required. Some of the options, in particular, those that are
-      compatible  with Perl, can also be set and unset from within
-      the pattern (see the detailed description of regular expres-
-      sions below). For these options, the contents of the options
-      argument specifies their initial settings at  the  start  of
-      compilation  and  execution. The PCRE_ANCHORED option 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 message. The offset from the start
-      of  the  pattern  to  the  character  where  the  error  was
-      discovered   is   placed  in  the  variable  pointed  to  by
-      erroffset, which must not be NULL. If it  is,  an  immediate
-      error is given.
-      If the final  argument,  tableptr,  is  NULL,  PCRE  uses  a
-      default  set  of character tables which are built when it is
-      compiled, using the default C  locale.  Otherwise,  tableptr
-      must  be  the result of a call to pcre_maketables(). See the
-      section on locale support below.
-      The following option bits are defined in the header file:
-        PCRE_ANCHORED
-      If this bit is set, the pattern is forced to be  "anchored",
-      that is, it is constrained to match only at the start of the
-      string which is being searched (the "subject string").  This
-      effect can also be achieved by appropriate constructs in the
-      pattern itself, which is the only way to do it in Perl.
-        PCRE_CASELESS
-      If this bit is set, letters in the pattern match both  upper
-      and  lower  case  letters.  It  is  equivalent  to Perl's /i
-      option.
-        PCRE_DOLLAR_ENDONLY
-      If this bit is set, a dollar metacharacter  in  the  pattern
-      matches  only at the end of the subject string. Without this
-      option, a dollar also matches immediately before  the  final
-      character  if it is a newline (but not before any other new-
-      lines).  The  PCRE_DOLLAR_ENDONLY  option  is   ignored   if
-      PCRE_MULTILINE is set. There is no equivalent to this option
-      in Perl.
-        PCRE_DOTALL
-      If this bit is  set,  a  dot  metacharater  in  the  pattern
-      matches all characters, including newlines. Without it, new-
-      lines are excluded. This option is equivalent to  Perl's  /s
-      option.  A negative class such as [^a] always matches a new-
-      line character, independent of the setting of this option.
-        PCRE_EXTENDED
-      If this bit is set, whitespace data characters in  the  pat-
-      tern  are  totally  ignored  except when escaped or inside a
-      character class, and characters between an unescaped #  out-
-      side  a  character  class  and  the  next newline character,
-      inclusive, are also ignored. This is equivalent to Perl's /x
-      option,  and  makes  it  possible to include comments inside
-      complicated patterns. Note, however, that this applies  only
-      to  data  characters. Whitespace characters may never appear
-      within special character sequences in a pattern, for example
-      within  the sequence (?( which introduces a conditional sub-
-      pattern.
-        PCRE_EXTRA
-      This option was invented in  order  to  turn  on  additional
-      functionality of PCRE that is incompatible with Perl, but it
-      is currently of very little use. When set, any backslash  in
-      a  pattern  that is followed by a letter that has no special
-      meaning causes an error, thus reserving  these  combinations
-      for  future  expansion.  By default, as in Perl, a backslash
-      followed by a letter with no special meaning is treated as a
-      literal.  There  are at present no other features controlled
-      by this option. It can also be set by a (?X) option  setting
-      within a pattern.
-        PCRE_MULTILINE
-      By default, PCRE treats the subject string as consisting  of
-      a  single "line" of characters (even if it actually contains
-      several newlines). The "start  of  line"  metacharacter  (^)
-      matches  only  at the start of the string, 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"  constructs match immediately following or immedi-
-      ately before any newline  in  the  subject  string,  respec-
-      tively,  as  well  as  at  the  very  start and end. This is
-      equivalent to Perl's /m option. If there are no "\n" charac-
-      ters  in  a subject string, or no occurrences of ^ or $ in a
-      pattern, setting PCRE_MULTILINE has no effect.
-        PCRE_UNGREEDY
-      This option inverts the "greediness" of the  quantifiers  so
-      that  they  are  not greedy by default, but become greedy if
-      followed by "?". It is not compatible with Perl. It can also
-      be set by a (?U) option setting within the pattern.
-        PCRE_UTF8
-      This option causes PCRE to regard both the pattern  and  the
-      subject  as strings of UTF-8 characters instead of just byte
-      strings. However, it is available  only  if  PCRE  has  been
-      built  to  include  UTF-8  support.  If not, the use of this
-      option provokes an error. Support for UTF-8 is new,  experi-
-      mental,  and incomplete.  Details of exactly what it entails
-      are given below.
+        pcre *pcre_compile(const char *pattern, int options,
+             const char **errptr, int *erroffset,
+             const unsigned char *tableptr);
+        The  function  pcre_compile()  is  called  to compile a pattern into an
+        internal form. 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 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 when
+        it is no longer required.
+        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-
+        ment, which is an address (see below).
+        The options argument contains independent bits that affect the compila-
+        tion. It should be zero if  no  options  are  required.  The  available
+        options  are  described  below. Some of them, in particular, those that
+        are compatible with Perl, can also be set and  unset  from  within  the
+        pattern  (see  the  detailed  description in the pcrepattern documenta-
+        tion). For these options, the contents of the options  argument  speci-
+        fies  their initial settings at the start of compilation and execution.
+        The PCRE_ANCHORED option 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. The offset from the start of the pattern to the  character  where
+        the  error  was  discovered  is  placed  in  the variable pointed to by
+        erroffset, which must not be NULL. If it  is,  an  immediate  error  is
+        given.
+        If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
+        character tables that are  built  when  PCRE  is  compiled,  using  the
+        default  C  locale.  Otherwise, tableptr must be an address that is the
+        result of a call to pcre_maketables(). This value is  stored  with  the
+        compiled  pattern,  and used again by pcre_exec(), unless another table
+        pointer is passed to it. For more discussion, see the section on locale
+        support below.
+        This  code  fragment  shows a typical straightforward call to pcre_com-
+        pile():
+          pcre *re;
+          const char *error;
+          int erroffset;
+          re = pcre_compile(
+            "^A.*Z",          /* the pattern */
+,                /* default options */
+            &error,           /* for error message */
+            &erroffset,       /* for error offset */
+            NULL);            /* use default character tables */
+        The following names for option bits are defined in  the  pcre.h  header
+        file:
+          PCRE_ANCHORED
+        If this bit is set, the pattern is forced to be "anchored", that is, it
+        is constrained to match only at the first matching point in the  string
+        that  is being searched (the "subject string"). This effect can also be
+        achieved by appropriate constructs in the pattern itself, which is  the
+        only way to do it in Perl.
+          PCRE_AUTO_CALLOUT
+        If this bit is set, pcre_compile() automatically inserts callout items,
+        all with number 255, before each pattern item. For  discussion  of  the
+        callout facility, see the pcrecallout documentation.
+          PCRE_CASELESS
+        If  this  bit is set, letters in the pattern match both upper and lower
+        case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
+        changed  within  a  pattern  by  a (?i) option setting. When running in
+        UTF-8 mode, case support for high-valued characters is  available  only
+        when PCRE is built with Unicode character property support.
+          PCRE_DOLLAR_ENDONLY
+        If  this bit is set, a dollar metacharacter in the pattern matches only
+        at the end of the subject string. Without this option,  a  dollar  also
+        matches  immediately before the final character if it is a newline (but
+        not before any  other  newlines).  The  PCRE_DOLLAR_ENDONLY  option  is
+        ignored if PCRE_MULTILINE is set. There is no equivalent to this option
+        in Perl, and no way to set it within a pattern.
+          PCRE_DOTALL
+        If this bit is set, a dot metacharater in the pattern matches all char-
+        acters,  including  newlines.  Without  it, newlines are excluded. This
+        option is equivalent to Perl's /s option, and it can be changed  within
+        a  pattern  by  a  (?s)  option  setting. A negative class such as [^a]
+        always matches a newline character, independent of the setting of  this
+        option.
+          PCRE_EXTENDED
+        If  this  bit  is  set,  whitespace  data characters in the pattern are
+        totally ignored except  when  escaped  or  inside  a  character  class.
+        Whitespace  does  not  include the VT character (code 11). In addition,
+        characters between an unescaped # outside a  character  class  and  the
+        next newline character, inclusive, are also ignored. This is equivalent
+        to Perl's /x option, and it can be changed within a pattern by  a  (?x)
+        option setting.
+        This  option  makes  it possible to include comments inside complicated
+        patterns.  Note, however, that this applies only  to  data  characters.
+        Whitespace   characters  may  never  appear  within  special  character
+        sequences in a pattern, for  example  within  the  sequence  (?(  which
+        introduces a conditional subpattern.
+          PCRE_EXTRA
+        This  option  was invented in order to turn on additional functionality
+        of PCRE that is incompatible with Perl, but it  is  currently  of  very
+        little  use. When set, any backslash in a pattern that is followed by a
+        letter that has no special meaning  causes  an  error,  thus  reserving
+        these  combinations  for  future  expansion.  By default, as in Perl, a
+        backslash followed by a letter with no special meaning is treated as  a
+        literal.  There  are  at  present  no other features controlled by this
+        option. It can also be set by a (?X) option setting within a pattern.
+          PCRE_MULTILINE
+        By default, PCRE treats the subject string as consisting  of  a  single
+        line  of characters (even if it actually contains newlines). The "start
+        of line" metacharacter (^) matches only at the  start  of  the  string,
+        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"
+        constructs match immediately following or immediately before  any  new-
+        line  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  changed
+        within a pattern by a (?m) option setting. If there are no "\n" charac-
+        ters in a subject string, or no occurrences of ^ or  $  in  a  pattern,
+        setting PCRE_MULTILINE has no effect.
+          PCRE_NO_AUTO_CAPTURE
+        If this option is set, it disables the use of numbered capturing paren-
+        theses in the pattern. Any opening parenthesis that is not followed  by
+        ?  behaves as if it were followed by ?: but named parentheses can still
+        be used for capturing (and they acquire  numbers  in  the  usual  way).
+        There is no equivalent of this option in Perl.
+          PCRE_UNGREEDY
+        This  option  inverts  the "greediness" of the quantifiers so that they
+        are not greedy by default, but become greedy if followed by "?". It  is
+        not  compatible  with Perl. It can also be set by a (?U) option setting
+        within the pattern.
+          PCRE_UTF8
+        This option causes PCRE to regard both the pattern and the  subject  as
+        strings  of  UTF-8 characters instead of single-byte character strings.
+        However, it is available only when PCRE is built to include UTF-8  sup-
+        port.  If not, the use of this option provokes an error. Details of how
+        this option changes the behaviour of PCRE are given in the  section  on
+        UTF-8 support in the main pcre page.
+          PCRE_NO_UTF8_CHECK
+        When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
+        automatically checked. If an invalid UTF-8 sequence of bytes is  found,
+        pcre_compile()  returns an error. If you already know that your pattern
+        is valid, and you want to skip this check for performance reasons,  you
+        can  set  the  PCRE_NO_UTF8_CHECK option. When it is set, the effect of
+        passing an invalid UTF-8 string as a pattern is undefined. It may cause
+        your  program  to  crash.   Note that this option can also be passed to
+        pcre_exec(),  to  suppress  the  UTF-8  validity  checking  of  subject
+        strings.
  STUDYING A PATTERN
-      When a 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 pattern as its first argument, and
-      returns a  pointer  to  a  pcre_extra  block  (another  void
-      typedef)  containing  additional  information about the pat-
-      tern; this can be passed to pcre_exec().  If  no  additional
-      information is available, NULL is returned.
-      The second argument contains option  bits.  At  present,  no
-      options  are  defined  for  pcre_study(),  and this argument
-      should always be zero.
-      The third argument for pcre_study() is a pointer to an error
-      message. If studying succeeds (even if no data is returned),
-      the variable it points to  is  set  to  NULL.  Otherwise  it
-      points to a textual error message.
-      At present, studying a  pattern  is  useful  only  for  non-
-      anchored  patterns  that do not have a single fixed starting
-      character. A  bitmap  of  possible  starting  characters  is
-      created.
+        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
+        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-
+        tern as its first argument. If studying the pattern produces additional
+        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
+        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
+        that  can  be  set  by the caller before the block is passed; these are
+        described below in the section on matching a pattern.
+        If studying the pattern does not produce  any  additional  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
+        its own pcre_extra block.
+        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.
+        If  studying  succeeds  (even  if no data is returned), the variable it
+        points to is set to NULL. Otherwise it points to a textual  error  mes-
+        sage.  You should therefore test the error pointer for NULL after call-
+        ing pcre_study(), to be sure that it has run successfully.
+        This is a typical call to pcre_study():
+          pcre_extra *pe;
+          pe = pcre_study(
+            re,             /* result of pcre_compile() */
+,              /* no options exist */
+            &error);        /* set to NULL or points to a message */
+        At present, studying a pattern is useful only for non-anchored patterns
+        that  do not have a single fixed starting character. A bitmap of possi-
+        ble starting bytes is created.
  LOCALE SUPPORT
-      PCRE handles caseless matching, and determines whether char-
-      acters  are  letters, digits, or whatever, by reference to a
-      set of tables. The library contains a default set of  tables
-      which  is  created in the default C locale when PCRE is com-
-      piled.  This  is   used   when   the   final   argument   of
-      pcre_compile()  is NULL, and is sufficient for many applica-
-      tions.
-      An alternative set of tables can, however, be supplied. Such
-      tables  are built by calling the pcre_maketables() function,
-      which has no arguments, in the relevant locale.  The  result
-      can  then be passed to pcre_compile() as often as necessary.
-      For example, to build and use tables  that  are  appropriate
-      for  the French locale (where accented characters with codes
-      greater than 128 are treated as letters), the following code
-      could be used:
-        setlocale(LC_CTYPE, "fr");
-        tables = pcre_maketables();
-        re = pcre_compile(..., tables);
-      The  tables  are  built  in  memory  that  is  obtained  via
-      pcre_malloc.  The  pointer that is passed to pcre_compile is
-      saved with the compiled pattern, and  the  same  tables  are
-      used  via this pointer by pcre_study() and pcre_exec(). Thus
-      for any single pattern, compilation, studying  and  matching
-      all happen in the same locale, but different patterns can be
-      compiled in different locales. It is the caller's  responsi-
-      bility  to  ensure  that  the  memory  containing the tables
-      remains available for as long as it is needed.
+        PCRE handles caseless matching, and determines whether  characters  are
+        letters,  digits, or whatever, by reference to a set of tables, indexed
+        by character value. (When running in UTF-8 mode, this applies  only  to
+        characters  with  codes  less than 128. Higher-valued codes never match
+        escapes such as \w or \d, but can be tested with \p if  PCRE  is  built
+        with Unicode character property support.)
+        An  internal set of tables is created in the default C locale when PCRE
+        is built. This is used when the final  argument  of  pcre_compile()  is
+        NULL,  and  is  sufficient for many applications. An alternative set of
+        tables can, however, be supplied. These may be created in  a  different
+        locale  from the default. As more and more applications change to using
+        Unicode, the need for this locale support is expected to die away.
+        External tables are built by calling  the  pcre_maketables()  function,
+        which  has no arguments, in the relevant locale. The result can then be
+        passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
+        example,  to  build  and use tables that are appropriate for the French
+        locale (where accented characters with  values  greater  than  128  are
+        treated as letters), the following code could be used:
+          setlocale(LC_CTYPE, "fr_FR");
+          tables = pcre_maketables();
+          re = pcre_compile(..., tables);
+        When  pcre_maketables()  runs,  the  tables are built in memory that is
+        obtained via pcre_malloc. It is the caller's responsibility  to  ensure
+        that  the memory containing the tables remains available for as long as
+        it is needed.
+        The pointer that is passed to pcre_compile() is saved with the compiled
+        pattern,  and the same tables are used via this pointer by pcre_study()
+        and normally also by pcre_exec(). Thus, by default, for any single pat-
+        tern, compilation, studying and matching all happen in the same locale,
+        but different patterns can be compiled in different locales.
+        It is possible to pass a table pointer or NULL (indicating the  use  of
+        the  internal  tables)  to  pcre_exec(). Although not intended for this
+        purpose, this facility could be used to match a pattern in a  different
+        locale from the one in which it was compiled. Passing table pointers at
+        run time is discussed below in the section on matching a pattern.
  INFORMATION ABOUT A PATTERN
-      The pcre_fullinfo() function  returns  information  about  a
-      compiled pattern. It replaces the obsolete pcre_info() func-
-      tion, which is nevertheless retained for backwards compabil-
-      ity (and is documented below).
-      The first argument for pcre_fullinfo() is a pointer  to  the
-      compiled  pattern.  The  second  argument  is  the result of
-      pcre_study(), or NULL if the pattern was  not  studied.  The
-      third  argument  specifies  which  piece  of  information is
-      required, while the fourth argument is a pointer to a  vari-
-      able  to receive the data. The yield of the function is zero
-      for success, or one of the following negative numbers:
-        PCRE_ERROR_NULL       the argument code was NULL
-                              the argument where was NULL
-        PCRE_ERROR_BADMAGIC   the "magic number" was not found
-        PCRE_ERROR_BADOPTION  the value of what was invalid
-      The possible values for the third argument  are  defined  in
-      pcre.h, and are as follows:
-        PCRE_INFO_OPTIONS
-      Return a copy of the options with which the pattern was com-
-      piled.  The fourth argument should point to au unsigned long
-      int variable. These option bits are those specified  in  the
-      call  to  pcre_compile(),  modified  by any top-level option
-      settings  within  the   pattern   itself,   and   with   the
-      PCRE_ANCHORED  bit  forcibly  set if the form of the pattern
-      implies that it can match only at the  start  of  a  subject
-      string.
-        PCRE_INFO_SIZE
-      Return the size of the compiled pattern, that is, the  value
-      that  was  passed as the argument to pcre_malloc() when PCRE
-      was getting memory in which to place the compiled data.  The
-      fourth argument should point to a size_t variable.
-        PCRE_INFO_CAPTURECOUNT
-      Return the number of capturing subpatterns in  the  pattern.
-      The fourth argument should point to an int variable.
-        PCRE_INFO_BACKREFMAX
-      Return the number of  the  highest  back  reference  in  the
-      pattern.  The  fourth  argument should point to an int vari-
-      able. Zero is returned if there are no back references.
-        PCRE_INFO_FIRSTCHAR
-      Return information about the first character of any  matched
-      string,  for  a  non-anchored  pattern.  If there is a fixed
-      first   character,   e.g.   from   a   pattern    such    as
-      (cat|cow|coyote),  it  is returned in the integer pointed to
-      by where. Otherwise, if either
-      (a) the pattern was compiled with the PCRE_MULTILINE option,
-      and every branch starts with "^", or
-      (b) every  branch  of  the  pattern  starts  with  ".*"  and
-      PCRE_DOTALL is not set (if it were set, the pattern would be
-      anchored),
-      -1 is returned, indicating that the pattern matches only  at
-      the  start  of a subject string or after any "\n" within the
-      string. Otherwise -2 is returned.  For anchored patterns, -2
-      is returned.
-        PCRE_INFO_FIRSTTABLE
-      If the pattern was studied, and this resulted  in  the  con-
-      struction of a 256-bit table indicating a fixed set of char-
-      acters for the first character in  any  matching  string,  a
-      pointer   to  the  table  is  returned.  Otherwise  NULL  is
-      returned. The fourth argument should point  to  an  unsigned
-      char * variable.
-        PCRE_INFO_LASTLITERAL
-      For a non-anchored pattern, return the value of  the  right-
-      most  literal  character  which  must  exist  in any matched
-      string, other than at its start. The fourth argument  should
-      point  to an int variable. If there is no such character, or
-      if the pattern is anchored, -1 is returned. For example, for
-      the pattern /a\d+z\d+/ the returned value is 'z'.
-      The pcre_info() function is now obsolete because its  inter-
-      face  is  too  restrictive  to return all the available data
-      about  a  compiled  pattern.   New   programs   should   use
-      pcre_fullinfo()  instead.  The  yield  of pcre_info() is the
-      number of capturing subpatterns, or  one  of  the  following
-      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 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  NULL, it is used to pass back information about the
-      first    character    of    any    matched    string    (see
-      PCRE_INFO_FIRSTCHAR above).
+        int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
+             int what, void *where);
+        The pcre_fullinfo() function returns information about a compiled  pat-
+        tern. It replaces the obsolete pcre_info() function, which is neverthe-
+        less retained for backwards compability (and is documented below).
+        The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
+        pattern.  The second argument is the result of pcre_study(), or NULL if
+        the pattern was not studied. The third argument specifies  which  piece
+        of  information  is required, and the fourth argument is a pointer to a
+        variable to receive the data. The yield of the  function  is  zero  for
+        success, or one of the following negative numbers:
+          PCRE_ERROR_NULL       the argument code was NULL
+                                the argument where was NULL
+          PCRE_ERROR_BADMAGIC   the "magic number" was not found
+          PCRE_ERROR_BADOPTION  the value of what was invalid
+        The  "magic  number" is placed at the start of each compiled pattern as
+        an simple check against passing an arbitrary memory pointer. Here is  a
+        typical  call  of pcre_fullinfo(), to obtain the length of the compiled
+        pattern:
+          int rc;
+          unsigned long int length;
+          rc = pcre_fullinfo(
+            re,               /* result of pcre_compile() */
+            pe,               /* result of pcre_study(), or NULL */
+            PCRE_INFO_SIZE,   /* what is required */
+            &length);         /* where to put the data */
+        The possible values for the third argument are defined in  pcre.h,  and
+        are as follows:
+          PCRE_INFO_BACKREFMAX
+        Return  the  number  of  the highest back reference in the pattern. The
+        fourth argument should point to an int variable. Zero  is  returned  if
+        there are no back references.
+          PCRE_INFO_CAPTURECOUNT
+        Return  the  number of capturing subpatterns in the pattern. The fourth
+        argument should point to an int variable.
+          PCRE_INFO_DEFAULTTABLES
+        Return a pointer to the internal default character tables within  PCRE.
+        The  fourth  argument should point to an unsigned char * variable. This
+        information call is provided for internal use by the pcre_study() func-
+        tion.  External  callers  can  cause PCRE to use its internal tables by
+        passing a NULL table pointer.
+          PCRE_INFO_FIRSTBYTE
+        Return information about the first byte of any matched  string,  for  a
+        non-anchored    pattern.    (This    option    used    to   be   called
+        PCRE_INFO_FIRSTCHAR; the old name is  still  recognized  for  backwards
+        compatibility.)
+        If  there  is  a  fixed first byte, for example, from a pattern such as
+        (cat|cow|coyote), it is returned in the integer pointed  to  by  where.
+        Otherwise, if either
+        (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
+        branch starts with "^", or
+        (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
+        set (if it were set, the pattern would be anchored),
+        -1  is  returned, indicating that the pattern matches only at the start
+        of a subject string or after any newline within the  string.  Otherwise
+        -2 is returned. For anchored patterns, -2 is returned.
+          PCRE_INFO_FIRSTTABLE
+        If  the pattern was studied, and this resulted in the construction of a
+-bit table indicating a fixed set of bytes for the first byte in any
+        matching  string, a pointer to the table is returned. Otherwise NULL is
+        returned. The fourth argument should point to an unsigned char *  vari-
+        able.
+          PCRE_INFO_LASTLITERAL
+        Return  the  value of the rightmost literal byte that must exist in any
+        matched string, other than at its  start,  if  such  a  byte  has  been
+        recorded. The fourth argument should point to an int variable. If there
+        is no such byte, -1 is returned. For anchored patterns, a last  literal
+        byte  is  recorded only if it follows something of variable length. For
+        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_NAMECOUNT
+          PCRE_INFO_NAMEENTRYSIZE
+          PCRE_INFO_NAMETABLE
+        PCRE  supports the use of named as well as numbered capturing parenthe-
+        ses. The names are just an additional way of identifying the  parenthe-
+        ses,  which  still  acquire  numbers.  A  convenience  function  called
+        pcre_get_named_substring() is provided  for  extracting  an  individual
+        captured  substring  by  name.  It is also possible to extract the data
+        directly, by first converting the name to a number in order  to  access
+        the  correct  pointers in the output vector (described with pcre_exec()
+        below). To do the conversion, you need to use the  name-to-number  map,
+        which is described by these three values.
+        The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
+        gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
+        of  each  entry;  both  of  these  return  an int value. The entry size
+        depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
+        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.
+        For  example,  consider  the following pattern (assume PCRE_EXTENDED is
+        set, so white space - including newlines - is ignored):
+          (?P<date> (?P<year>(\d\d)?\d\d) -
+          (?P<month>\d\d) - (?P<day>\d\d) )
+        There are four named subpatterns, so the table has  four  entries,  and
+        each  entry  in the table is eight bytes long. The table is as follows,
+        with non-printing bytes shows in hexadecimal, and undefined bytes shown
+        as ??:
+01 d  a  t  e  00 ??
+05 d  a  y  00 ?? ??
+04 m  o  n  t  h  00
+02 y  e  a  r  00 ??
+        When  writing  code  to  extract  data from named subpatterns using the
+        name-to-number map, remember that the length of each entry is likely to
+        be different for each compiled pattern.
+          PCRE_INFO_OPTIONS
+        Return  a  copy of the options with which the pattern was compiled. The
+        fourth argument should point to an unsigned long  int  variable.  These
+        option bits are those specified in the call to pcre_compile(), modified
+        by any top-level option settings within the pattern itself.
+        A pattern is automatically anchored by PCRE if  all  of  its  top-level
+        alternatives begin with one of the following:
+          ^     unless PCRE_MULTILINE is set
+          \A    always
+          \G    always
+          .*    if PCRE_DOTALL is set and there are no back
+                  references to the subpattern in which .* appears
+        For such patterns, the PCRE_ANCHORED bit is set in the options returned
+        by pcre_fullinfo().
+          PCRE_INFO_SIZE
+        Return the size of the compiled pattern, that is, the  value  that  was
+        passed as the argument to pcre_malloc() when PCRE was getting memory in
+        which to place the compiled data. The fourth argument should point to a
+        size_t variable.
+          PCRE_INFO_STUDYSIZE
+        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
+        variable.
+ 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
+        restrictive to return all the available data about a compiled  pattern.
+        New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
+        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
+        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
+        NULL, it is used to pass back information about the first character  of
+        any matched string (see PCRE_INFO_FIRSTBYTE above).
  MATCHING A PATTERN
-      The function pcre_exec() is called to match a subject string
-      against  a pre-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 argument. Otherwise this
-      must be NULL.
-      The PCRE_ANCHORED option can be passed in the options  argu-
-      ment,  whose unused bits must be zero. However, if a pattern
-      was  compiled  with  PCRE_ANCHORED,  or  turned  out  to  be
-      anchored  by  virtue  of  its  contents,  it  cannot be made
-      unachored at matching time.
-      There are also three further options that can be set only at
-      matching time:
-        PCRE_NOTBOL
-      The first character of the string is not the beginning of  a
-      line,  so  the  circumflex  metacharacter  should  not match
-      before it. Setting this without PCRE_MULTILINE  (at  compile
-      time) causes circumflex never to match.
-        PCRE_NOTEOL
-      The end of the string is not the end of a line, so the  dol-
-      lar  metacharacter should not match it nor (except in multi-
-      line mode) a newline immediately  before  it.  Setting  this
-      without PCRE_MULTILINE (at compile time) causes dollar never
-      to match.
-        PCRE_NOTEMPTY
-      An empty string is not considered to be  a  valid  match  if
-      this  option  is  set. If there are alternatives in the pat-
-      tern, they are tried. If  all  the  alternatives  match  the
-      empty  string,  the  entire match fails. For example, if the
-      pattern
-        a?b?
-      is applied to a string not beginning with  "a"  or  "b",  it
-      matches  the  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 occurrences of "a" or "b".
-      Perl has no direct equivalent of PCRE_NOTEMPTY, 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
-      offset  with  PCRE_NOTEMPTY  set,  and then if that fails by
-      advancing the starting offset  (see  below)  and  trying  an
-      ordinary match again.
-      The subject string is passed as  a  pointer  in  subject,  a
-      length  in  length,  and  a  starting offset in startoffset.
-      Unlike the pattern string, it may contain binary zero  char-
-      acters.  When  the starting offset is zero, the search for a
-      match starts 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 success.  Setting startoffset differs
-      from  just  passing  over  a  shortened  string  and setting
-      PCRE_NOTBOL in the case of a pattern that  begins  with  any
-      kind of lookbehind. For example, consider the pattern
-        \Biss\B
-      which finds occurrences of "iss" in the middle of words. (\B
-      matches only if the current position in the subject is not a
-      word boundary.) When applied to the string "Mississipi"  the
-      first  call  to  pcre_exec()  finds the first occurrence. If
-      pcre_exec() is called again with just the remainder  of  the
-      subject,  namely  "issipi", it does not match, because \B is
-      always false at the start of the subject, which is deemed to
-      be  a  word  boundary. However, if pcre_exec() is passed the
-      entire string again, but with startoffset set to 4, it finds
-      the  second  occurrence  of "iss" because it is able to look
-      behind the starting point to discover that it is preceded by
-      a letter.
-      If a non-zero starting offset is passed when the pattern  is
-      anchored, one attempt to match at the given offset is tried.
-      This can only succeed if the pattern does  not  require  the
-      match to be at the start of the subject.
-      In general, a pattern matches a certain portion of the  sub-
-      ject,  and  in addition, further substrings from the subject
-      may be picked out by parts of  the  pattern.  Following  the
-      usage  in  Jeffrey Friedl's book, this is called "capturing"
-      in what follows, and the phrase  "capturing  subpattern"  is
-      used for a fragment of a pattern that picks out a substring.
-      PCRE supports several other kinds of  parenthesized  subpat-
-      tern that do not cause substrings to be captured.
-      Captured substrings are returned to the caller via a  vector
-      of  integer  offsets whose address is passed in ovector. The
-      number of elements in the vector is passed in ovecsize.  The
-      first two-thirds of the vector is used to pass back captured
-      substrings, each substring using a  pair  of  integers.  The
-      remaining  third  of  the  vector  is  used  as workspace by
-      pcre_exec() while matching capturing subpatterns, and is not
-      available for passing back information. The length passed in
-      ovecsize should always be a multiple of three. If it is not,
-      it is rounded down.
-      When a match has been 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  substring,  and  the
-      second is set to the offset of the first character after the
-      end of a substring. The first  pair,  ovector[0]  and  ovec-
-      tor[1],  identify  the portion of the subject string matched
-      by the entire pattern. The next pair is used for  the  first
-      capturing  subpattern,  and  so  on.  The  value returned by
-      pcre_exec() is the number of pairs that have  been  set.  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.
-      Some convenience functions are provided for  extracting  the
-      captured substrings as separate strings. These are described
-      in the following section.
-      It is possible for an 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) subpatterns 1 and 3
-      are matched, but 2 is not. When this  happens,  both  offset
-      values corresponding to the unused subpattern are set to -1.
-      If a capturing subpattern is matched repeatedly, it  is  the
-      last  portion  of  the  string  that  it  matched  that gets
-      returned.
-      If the vector is too small to hold  all  the  captured  sub-
-      strings,  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 offsets are not of interest,
-      pcre_exec() may be called with ovector passed  as  NULL  and
-      ovecsize  as  zero.  However,  if  the pattern contains back
-      references and the ovector isn't big enough to remember  the
-      related  substrings,  PCRE  has to get additional memory for
-      use during matching. Thus it is usually advisable to  supply
-      an ovector.
-      Note that pcre_info() can be used to find out how many  cap-
-      turing  subpatterns  there  are  in  a compiled pattern. The
-      smallest size for 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.
-      If pcre_exec() fails, it returns a negative number. The fol-
-      lowing are defined in the header file:
-        PCRE_ERROR_NOMATCH        (-1)
-      The subject string did not match the pattern.
-        PCRE_ERROR_NULL           (-2)
-      Either code or subject was passed as NULL,  or  ovector  was
-      NULL and ovecsize was not zero.
-        PCRE_ERROR_BADOPTION      (-3)
-      An unrecognized bit was set in the options argument.
-        PCRE_ERROR_BADMAGIC       (-4)
-      PCRE stores a 4-byte "magic number" at the start of the com-
-      piled  code,  to  catch  the  case  when it is passed a junk
-      pointer. This is the error it gives when  the  magic  number
-      isn't present.
-        PCRE_ERROR_UNKNOWN_NODE   (-5)
-      While running the pattern match, an unknown item was encoun-
-      tered in the 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  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 purpose. If the call via
-      pcre_malloc() fails, this error  is  given.  The  memory  is
-      freed at the end of matching.
- EXTRACTING CAPTURED SUBSTRINGS
-      Captured substrings can be accessed directly  by  using  the
- SunOS 5.8                 Last change:                         12
-      offsets returned by pcre_exec() in ovector. For convenience,
-      the functions  pcre_copy_substring(),  pcre_get_substring(),
-      and  pcre_get_substring_list()  are  provided for extracting
-      captured  substrings  as  new,   separate,   zero-terminated
-      strings.   A  substring  that  contains  a  binary  zero  is
-      correctly extracted and has a further zero added on the end,
-      but the result does not, of course, function as a C string.
-      The first three arguments are the same for all  three  func-
-      tions:  subject  is  the  subject string which 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
-      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 ran out of space in  ovec-
-      tor,  the  value passed as stringcount should be the size of
-      the vector divided by three.
-      The functions pcre_copy_substring() and pcre_get_substring()
-      extract a single substring, whose number is given as string-
-      number. A value of zero extracts the substring that  matched
-      the entire pattern, while higher values extract the captured
-      substrings. For pcre_copy_substring(), the string is  placed
-      in  buffer,  whose  length is given by buffersize, while for
-      pcre_get_substring() a new block of memory is  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 terminating zero, or one of
-        PCRE_ERROR_NOMEMORY       (-6)
-      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  avail-
-      able  substrings  and builds a list of pointers to them. All
-      this is done in a single block of memory which  is  obtained
-      via pcre_malloc. The address 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 pointer.
-      The yield of the function is zero if all went well, or
-        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 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 empty string. This can be
-      distinguished  from  a  genuine  zero-length  substring   by
-      inspecting the appropriate offset in ovector, which is nega-
-      tive for unset substrings.
-      The  two  convenience  functions  pcre_free_substring()  and
-      pcre_free_substring_list()  can  be  used to free the memory
-      returned by  a  previous  call  of  pcre_get_substring()  or
-      pcre_get_substring_list(),  respectively.  They  do  nothing
-      more than call the function pointed to by  pcre_free,  which
-      of  course  could  be called directly from a C program. How-
-      ever, PCRE is used in some situations where it is linked via
-      a  special  interface  to another programming language which
-      cannot use pcre_free directly; it is for  these  cases  that
-      the functions are provided.
+        int pcre_exec(const pcre *code, const pcre_extra *extra,
+             const char *subject, int length, int startoffset,
+             int options, int *ovector, int ovecsize);
+        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
+        argument.
+        In most applications, the pattern will have been compiled (and  option-
+        ally  studied)  in the same process that calls pcre_exec(). However, it
+        is possible to save compiled patterns and study data, and then use them
+        later  in  different processes, possibly even on different hosts. For a
+        discussion about this, see the pcreprecompile documentation.
+        Here is an example of a simple call to pcre_exec():
+          int rc;
+          int ovector[30];
+          rc = pcre_exec(
+            re,             /* result of pcre_compile() */
+            NULL,           /* we didn't study the pattern */
+            "some string",  /* the subject string */
+,             /* the length of the subject string */
+,              /* start at offset 0 in the subject */
+,              /* default options */
+            ovector,        /* vector of integers for substring information */
+);            /* number of elements in the vector  (NOT  size  in
+        bytes) */
+    Extra data for pcre_exec()
+        If  the  extra argument is not NULL, it must point to a pcre_extra data
+        block. The pcre_study() function returns such a block (when it  doesn't
+        return  NULL), but you can also create one for yourself, and pass addi-
+        tional information in it. The fields in a pcre_extra block are as  fol-
+        lows:
+          unsigned long int flags;
+          void *study_data;
+          unsigned long int match_limit;
+          void *callout_data;
+          const unsigned char *tables;
+        The  flags  field  is a bitmap that specifies which of the other fields
+        are set. The flag bits are:
+          PCRE_EXTRA_STUDY_DATA
+          PCRE_EXTRA_MATCH_LIMIT
+          PCRE_EXTRA_CALLOUT_DATA
+          PCRE_EXTRA_TABLES
+        Other flag bits should be set to zero. The study_data field is  set  in
+        the  pcre_extra  block  that is returned by pcre_study(), together with
+        the appropriate flag bit. You should not set this yourself, but you may
+        add  to  the  block by setting the other fields and their corresponding
+        flag bits.
+        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
+        repeats.
+        Internally, PCRE uses a function called match() which it calls  repeat-
+        edly  (sometimes  recursively).  The  limit is imposed on the number of
+        times this function is called during a match, which has the  effect  of
+        limiting  the amount of recursion and backtracking that can take place.
+        For patterns that are not anchored, the count starts from zero for each
+        position in the subject string.
+        The  default  limit  for the library can be set when PCRE is built; the
+        default default is 10 million, which handles all but the  most  extreme
+        cases.  You  can  reduce  the  default  by  suppling pcre_exec() with a
+        pcre_extra block in which match_limit is set to a  smaller  value,  and
+        PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
+        exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
+        The pcre_callout field is used in conjunction with the  "callout"  fea-
+        ture, which is described in the pcrecallout documentation.
+        The  tables  field  is  used  to  pass  a  character  tables pointer to
+        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
+        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-
+        using  patterns  that  have been saved after compiling with an external
+        set of tables, because the external tables  might  be  at  a  different
+        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   only  bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,
+        PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
+          PCRE_ANCHORED
+        The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
+        matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
+        turned out to be anchored by virtue of its contents, it cannot be  made
+        unachored at matching time.
+          PCRE_NOTBOL
+        This option specifies that first character of the subject string is not
+        the beginning of a line, so the  circumflex  metacharacter  should  not
+        match  before it. Setting this without PCRE_MULTILINE (at compile time)
+        causes  circumflex  never  to  match.  This  option  affects  only  the
+        behaviour of the circumflex metacharacter. It does not affect \A.
+          PCRE_NOTEOL
+        This option specifies that the end of the subject string is not the end
+        of a line, so the dollar metacharacter should not match it nor  (except
+        in  multiline mode) a newline immediately before it. Setting this with-
+        out PCRE_MULTILINE (at compile time) causes dollar never to match. This
+        option  affects only the behaviour of the dollar metacharacter. It does
+        not affect \Z or \z.
+          PCRE_NOTEMPTY
+        An empty string is not considered to be a valid match if this option is
+        set.  If  there are alternatives in the pattern, they are tried. If all
+        the alternatives match the empty string, the entire  match  fails.  For
+        example, if the pattern
+          a?b?
+        is  applied  to  a string not beginning with "a" or "b", it matches the
+        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-
+        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
+        Perl's behaviour after matching a null string by first trying the match
+        again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
+        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
+        this in the pcredemo.c sample program.
+          PCRE_NO_UTF8_CHECK
+        When PCRE_UTF8 is set at compile time, the validity of the subject as a
+        UTF-8 string is automatically checked when pcre_exec() is  subsequently
+        called.   The  value  of  startoffset is also checked to ensure that it
+        points to the start of a UTF-8 character. If an invalid UTF-8  sequence
+        of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If
+        startoffset contains an  invalid  value,  PCRE_ERROR_BADUTF8_OFFSET  is
+        returned.
+        If  you  already  know that your subject is valid, and you want to skip
+        these   checks   for   performance   reasons,   you   can    set    the
+        PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
+        do this for the second and subsequent calls to pcre_exec() if  you  are
+        making  repeated  calls  to  find  all  the matches in a single subject
+        string. However, you should be  sure  that  the  value  of  startoffset
+        points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
+        set, the effect of passing an invalid UTF-8 string as a subject,  or  a
+        value  of startoffset that does not point to the start of a UTF-8 char-
+        acter, is undefined. Your program may crash.
+          PCRE_PARTIAL
+        This option turns on the  partial  matching  feature.  If  the  subject
+        string  fails to match the pattern, but at some point during the match-
+        ing process the end of the subject was reached (that  is,  the  subject
+        partially  matches  the  pattern and the failure to match occurred only
+        because there were not enough subject characters), pcre_exec()  returns
+        PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
+        used, there are restrictions on what may appear in the  pattern.  These
+        are discussed 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
+        length in length, and a starting byte offset in startoffset.  In  UTF-8
+        mode,  the  byte  offset  must point to the start of a UTF-8 character.
+        Unlike the pattern string, the subject may contain binary  zero  bytes.
+        When  the starting offset is zero, the search for a match starts 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-
+        cess.  Setting startoffset differs from just passing over  a  shortened
+        string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
+        with any kind of lookbehind. For example, consider the pattern
+          \Biss\B
+        which finds occurrences of "iss" in the middle of  words.  (\B  matches
+        only  if  the  current position in the subject is not a word boundary.)
+        When applied to the string "Mississipi" the first call  to  pcre_exec()
+        finds  the  first  occurrence. If pcre_exec() is called again with just
+        the remainder of the subject,  namely  "issipi",  it  does  not  match,
+        because \B is always false at the start of the subject, which is deemed
+        to be a word boundary. However, if pcre_exec()  is  passed  the  entire
+        string again, but with startoffset set to 4, it finds the second occur-
+        rence of "iss" because it is able to look behind the starting point  to
+        discover that it is preceded by a letter.
+        If  a  non-zero starting offset is passed when the pattern is anchored,
+        one attempt to match at the given offset is made. This can only succeed
+        if  the  pattern  does  not require the match to be at the start of the
+        subject.
+    How pcre_exec() returns captured substrings
+        In general, a pattern matches a certain portion of the subject, and  in
+        addition,  further  substrings  from  the  subject may be picked out by
+        parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
+        this  is  called "capturing" in what follows, and the phrase "capturing
+        subpattern" is used for a fragment of a pattern that picks out  a  sub-
+        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
+        offsets  whose  address is passed in ovector. The number of elements in
+        the vector is passed in ovecsize, which must be a non-negative  number.
+        Note: 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
+        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-
+        string, and the second is set to the  offset  of  the  first  character
+        after  the  end  of  a  substring. The first pair, ovector[0] and ovec-
+        tor[1], identify the portion of  the  subject  string  matched  by  the
+        entire  pattern.  The next pair is used for the first capturing subpat-
+        tern, and so on. The value returned by pcre_exec()  is  the  number  of
+        pairs  that  have  been set. 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.
+        Some  convenience  functions  are  provided for extracting the captured
+        substrings as separate strings. These are described  in  the  following
+        section.
+        It  is  possible  for  an 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)
+        subpatterns 1 and 3 are matched, but 2 is not. When this happens,  both
+        offset values corresponding to the unused subpattern are set to -1.
+        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,
+        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-
+        sets are not of interest, pcre_exec() may be called with ovector passed
+        as NULL and ovecsize as zero. However, if  the  pattern  contains  back
+        references  and  the  ovector is not big enough to remember the related
+        substrings, PCRE has to get additional memory for use during  matching.
+        Thus it is usually advisable to supply an ovector.
+        Note  that  pcre_info() can be used to find out how many capturing sub-
+        patterns there are in a compiled pattern. The smallest size for 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.
+    Return values from pcre_exec()
+        If pcre_exec() fails, it returns a negative number. The  following  are
+        defined in the header file:
+          PCRE_ERROR_NOMATCH        (-1)
+        The subject string did not match the pattern.
+          PCRE_ERROR_NULL           (-2)
+        Either  code  or  subject  was  passed as NULL, or ovector was NULL and
+        ovecsize was not zero.
+          PCRE_ERROR_BADOPTION      (-3)
+        An unrecognized bit was set in the options argument.
+          PCRE_ERROR_BADMAGIC       (-4)
+        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
+        gives when the magic number is not present.
+          PCRE_ERROR_UNKNOWN_NODE   (-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
+        overwriting of the compiled pattern.
+          PCRE_ERROR_NOMEMORY       (-6)
+        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
+        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(),
+        and  pcre_get_substring_list()  functions  (see  below).  It  is  never
+        returned by pcre_exec().
+          PCRE_ERROR_MATCHLIMIT     (-8)
+        The recursion and backtracking limit, as specified by  the  match_limit
+        field  in  a  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.
+        See the pcrecallout documentation for details.
+          PCRE_ERROR_BADUTF8        (-10)
+        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-
+        ter.
+          PCRE_ERROR_PARTIAL (-12)
+        The  subject  string did not match, but it did match partially. See the
+        pcrepartial documentation for details of partial matching.
+          PCRE_ERROR_BAD_PARTIAL (-13)
+        The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
+        items  that are not supported for partial matching. See the pcrepartial
+        documentation for details of partial matching.
+          PCRE_ERROR_INTERNAL (-14)
+        An unexpected internal error has occurred. This error could  be  caused
+        by a bug in PCRE or by overwriting of the compiled pattern.
+          PCRE_ERROR_BADCOUNT (-15)
+        This  error is given if the value of the ovecsize argument is negative.
+ EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
+        int pcre_copy_substring(const char *subject, int *ovector,
+             int stringcount, int stringnumber, char *buffer,
+             int buffersize);
+        int pcre_get_substring(const char *subject, int *ovector,
+             int stringcount, int stringnumber,
+             const char **stringptr);
+        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
+        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,
+        separate, zero-terminated strings. These functions identify  substrings
+        by  number.  The  next section describes functions for extracting named
+        substrings. 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 string.
+        The first three arguments are the same for all  three  of  these  func-
+        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
+        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  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
+        single  substring,  whose  number  is given as stringnumber. A value of
+        zero extracts the substring that matched the  entire  pattern,  whereas
+        higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
+        string(), the string is placed in buffer,  whose  length  is  given  by
+        buffersize,  while  for  pcre_get_substring()  a new block of memory is
+        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 terminating zero, or one of
+          PCRE_ERROR_NOMEMORY       (-6)
+        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-
+        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  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
+          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
+        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
+        empty string. This can be distinguished from a genuine zero-length sub-
+        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-
+        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
+        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-
+        cial  interface  to  another  programming  language  which  cannot  use
+        pcre_free directly; it is  for  these  cases  that  the  functions  are
+        provided.
+ EXTRACTING CAPTURED SUBSTRINGS BY NAME
+        int pcre_get_stringnumber(const pcre *code,
+             const char *name);
+        int pcre_copy_named_substring(const pcre *code,
+             const char *subject, int *ovector,
+             int stringcount, const char *stringname,
+             char *buffer, int buffersize);
+        int pcre_get_named_substring(const pcre *code,
+             const char *subject, int *ovector,
+             int stringcount, const char *stringname,
+             const char **stringptr);
+        To  extract a substring by name, you first have to find associated num-
+        ber.  For example, for this pattern
+          (a+)b(?<xxx>\d+)...
+        the number of the subpattern called "xxx" is 2. You can find the number
+        from the name by calling pcre_get_stringnumber(). The first argument is
+        the compiled 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 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
+        pcre_get_named_substring()  are  the  same  as  those for the similarly
+        named functions that extract by number. As these are described  in  the
+        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-
+        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
+        name-to-number translation table.
+        These  functions call pcre_get_stringnumber(), and if it succeeds, they
+        then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
+        ate.
+ Last updated: 09 September 2004
+ Copyright (c) 1997-2004 University of Cambridge.
+ -----------------------------------------------------------------------------
+ PCRE(3)                                                                PCRE(3)
- LIMITATIONS
-      There are some size limitations in PCRE but it is hoped that
-      they will never in practice be relevant.  The maximum length
-      of a compiled pattern is 65539 (sic) bytes.  All  values  in
-      repeating  quantifiers must be less than 65536.  The maximum
-      number of capturing subpatterns is 99.  The  maximum  number
-      of  all  parenthesized subpatterns, including capturing sub-
-      patterns, assertions, and other types of subpattern, is 200.
-      The maximum length of a subject string is the largest  posi-
-      tive number that an integer variable can hold. However, PCRE
-      uses recursion to handle subpatterns and indefinite  repeti-
-      tion.  This  means  that the available stack space may limit
-      the size of a subject string that can be processed  by  cer-
-      tain patterns.
- DIFFERENCES FROM PERL
-      The differences described here  are  with  respect  to  Perl
-.005.
-. By default, a whitespace character is any character  that
-      the  C  library  function isspace() recognizes, though it is
-      possible to compile PCRE  with  alternative  character  type
-      tables. Normally isspace() matches space, formfeed, newline,
-      carriage return, horizontal tab, and vertical tab. Perl 5 no
-      longer  includes vertical tab in its set of whitespace char-
-      acters. The \v escape that was in the Perl documentation for
-      a long time was never in fact recognized. However, the char-
-      acter itself was treated as whitespace at least up to 5.002.
-      In 5.004 and 5.005 it does not match \s.
-. PCRE does  not  allow  repeat  quantifiers  on  lookahead
-      assertions. Perl 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  looka-
-      head  assertions  are  counted,  but  their  entries  in the
-      offsets vector are never set. Perl sets its numerical  vari-
-      ables  from  any  such  patterns that are matched before the
-      assertion fails to match something (thereby succeeding), but
-      only  if  the negative lookahead assertion contains just one
-      branch.
-. Though binary zero characters are supported in  the  sub-
-      ject  string,  they  are  not  allowed  in  a pattern string
-      because it is passed as a normal  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,  \U,  \E, \Q. In fact these are implemented by
-      Perl's general string-handling and are not part of its  pat-
-      tern matching engine.
-. The Perl \G assertion is  not  supported  as  it  is  not
-      relevant to single pattern matches.
-. Fairly obviously, PCRE does not support the (?{code}) and
-      (?p{code})  constructions. However, there is some experimen-
-      tal support for recursive patterns using the  non-Perl  item
-      (?R).
-. There are at the time of writing some  oddities  in  Perl
-.005_02  concerned  with  the  settings of captured strings
-      when part of a pattern is repeated.  For  example,  matching
-      "aba"  against the pattern /^(a(b)?)+$/ sets $2 to the value
-      "b", but matching "aabbaa" against /^(aa(bb)?)+$/ leaves  $2
-      unset.    However,    if   the   pattern   is   changed   to
-      /^(aa(b(b))?)+$/ then $2 (and $3) are set.
-      In Perl 5.004 $2 is set in both cases, and that is also true
-      of PCRE. If in the future Perl changes to a consistent state
-      that is different, PCRE may change to follow.
-. Another as yet unresolved discrepancy  is  that  in  Perl
-.005_02  the  pattern /^(a)?(?(1)a|b)+$/ matches the string
-      "a", whereas in PCRE it does not.  However, in both Perl and
-      PCRE /^(a)?a/ matched against "a" leaves $1 unset.
-. PCRE  provides  some  extensions  to  the  Perl  regular
-      expression facilities:
-      (a) Although lookbehind assertions must match  fixed  length
-      strings,  each  alternative branch of a lookbehind assertion
-      can match a different length of string. Perl 5.005  requires
-      them all to have the same length.
-      (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 special meaning is faulted.
-      (d) If PCRE_UNGREEDY is set, the greediness of  the  repeti-
-      tion  quantifiers  is inverted, that is, by default they are
-      not greedy, but if followed by a question mark they are.
-      (e) PCRE_ANCHORED can be used to force a pattern to be tried
-      only at the start of the subject.
-      (f) The PCRE_NOTBOL, PCRE_NOTEOL, and PCRE_NOTEMPTY  options
-      for pcre_exec() have no Perl equivalents.
-      (g) The (?R) construct allows for recursive pattern matching
-      (Perl  5.6 can do this using the (?p{code}) construct, which
-      PCRE cannot of course support.)
- REGULAR EXPRESSION DETAILS
-      The syntax and semantics of  the  regular  expressions  sup-
-      ported  by PCRE are described below. Regular expressions are
-      also described in the Perl documentation and in a number  of
-      other  books,  some  of which have copious examples. Jeffrey
-      Friedl's  "Mastering  Regular  Expressions",  published   by
-      O'Reilly (ISBN 1-56592-257), covers them in great detail.
-      The description here is intended as reference documentation.
-      The basic operation of PCRE is on strings of bytes. However,
-      there is the beginnings of some support for UTF-8  character
-      strings.  To  use  this  support  you must configure PCRE to
-      include it, and then call pcre_compile() with the  PCRE_UTF8
-      option.  How  this affects the pattern matching is described
-      in the final section of this document.
-      A regular expression is a pattern that is matched against  a
-      subject string from left to right. Most characters stand for
-      themselves in a pattern, and match the corresponding charac-
-      ters in the subject. As a trivial example, the pattern
-        The quick brown fox
-      matches a portion of a subject string that is  identical  to
-      itself.  The  power  of  regular  expressions comes from the
-      ability to include alternatives and repetitions in the  pat-
-      tern.  These  are encoded in the pattern by the use of meta-
-      characters, which do not stand for  themselves  but  instead
-      are interpreted in some special way.
-      There are two different sets of meta-characters: those  that
-      are  recognized anywhere in the pattern except within square
-      brackets, and those that are recognized in square  brackets.
-      Outside square brackets, the meta-characters are as follows:
-        \      general escape character with several uses
-        ^      assert start of  subject  (or  line,  in  multiline
-      mode)
-        $      assert end of subject (or line, in multiline mode)
-        .      match any character except newline (by default)
-        [      start character class definition
-        |      start of alternative branch
-        (      start subpattern
-        )      end subpattern
-        ?      extends the meaning of (
-               also 0 or 1 quantifier
-               also quantifier minimizer
-        *      0 or more quantifier
-        +      1 or more quantifier
-        {      start min/max quantifier
-      Part of a pattern that is in square  brackets  is  called  a
-      "character  class".  In  a  character  class  the only meta-
-      characters are:
-        \      general escape character
-        ^      negate the class, but only if the first character
-        -      indicates character range
-        ]      terminates the character class
-      The following sections describe  the  use  of  each  of  the
-      meta-characters.
+ NAME
+        PCRE - Perl-compatible regular expressions
+ PCRE CALLOUTS
+        int (*pcre_callout)(pcre_callout_block *);
+        PCRE provides a feature called "callout", which is a means of temporar-
+        ily passing control to the caller of PCRE  in  the  middle  of  pattern
+        matching.  The  caller of PCRE provides an external function by putting
+        its entry point in the global variable pcre_callout. By  default,  this
+        variable contains NULL, which disables all calling out.
+        Within  a  regular  expression,  (?C) indicates the points at which the
+        external function is to be called.  Different  callout  points  can  be
+        identified  by  putting  a number less than 256 after the letter C. The
+        default value is zero.  For  example,  this  pattern  has  two  callout
+        points:
+          (?C1)eabc(?C2)def
+        If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
+        called, PCRE automatically  inserts  callouts,  all  with  number  255,
+        before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is
+        used with the pattern
+          A(\d{2}|--)
+        it is processed as if it were
+        (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255)
+        Notice that there is a callout before and after  each  parenthesis  and
+        alternation  bar.  Automatic  callouts  can  be  used  for tracking the
+        progress of pattern matching. The pcretest command has an  option  that
+        sets  automatic callouts; when it is used, the output indicates how the
+        pattern is matched. This is useful information when you are  trying  to
+        optimize the performance of a particular pattern.
+ 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
+        pattern is
+          ab(?C4)cd
+        PCRE knows that any matching string must contain the letter "d". If the
+        subject string is "abyz", the lack of "d" means that  matching  doesn't
+        ever  start,  and  the  callout is never reached. However, with "abyd",
+        though the result is still no match, the callout is obeyed.
+ THE CALLOUT INTERFACE
+        During matching, when PCRE reaches a callout point, the external  func-
+        tion  defined  by pcre_callout is called (if it is set). The only argu-
+        ment is a pointer to a pcre_callout block. This structure contains  the
+        following fields:
+          int          version;
+          int          callout_number;
+          int         *offset_vector;
+          const char  *subject;
+          int          subject_length;
+          int          start_match;
+          int          current_position;
+          int          capture_top;
+          int          capture_last;
+          void        *callout_data;
+          int          pattern_position;
+          int          next_item_length;
+        The  version  field  is an integer containing the version number of the
+        block format. The initial version was 0; the current version is 1.  The
+        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-
+        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
+        passed by the caller to pcre_exec(). The contents can be  inspected  in
+        order  to extract substrings that have been matched so far, in the same
+        way as for extracting substrings after a match has completed.
+        The subject and subject_length fields contain copies of the values that
+        were passed to pcre_exec().
+        The  start_match  field contains the offset within the subject at which
+        the current match attempt started. 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 match pointer.
+        The  capture_top field contains one more than the number of the highest
+        numbered captured substring so far. If no  substrings  have  been  cap-
+        tured, the value of capture_top is one.
+        The  capture_last  field  contains the number of the most recently cap-
+        tured substring. If no substrings have been captured, its value is  -1.
+        The  callout_data  field contains a value that is passed to pcre_exec()
+        by the caller specifically so that it can be passed back  in  callouts.
+        It  is  passed  in the pcre_callout field of the pcre_extra data struc-
+        ture. 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
+        structure in the pcreapi documentation.
+        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-
+        out structure. It contains the length of the next item to be matched in
+        the pattern string. When the callout immediately precedes  an  alterna-
+        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 that of the entire subpattern.
+        The  pattern_position  and next_item_length fields are intended to help
+        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
+        is zero, matching proceeds as normal. If  the  value  is  greater  than
+        zero,  matching  fails  at  the current point, but backtracking to test
+        other matching possibilities goes ahead, just as if a lookahead  asser-
+        tion  had  failed.  If  the value is less than zero, the match is aban-
+        doned, and pcre_exec() returns the negative value.
+        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
+        reserved  for  use  by callout functions; it will never be used by PCRE
+        itself.
+ Last updated: 09 September 2004
+ Copyright (c) 1997-2004 University of Cambridge.
+ -----------------------------------------------------------------------------
+ PCRE(3)                                                                PCRE(3)
+ NAME
+        PCRE - Perl-compatible regular expressions
+ 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  with
+        respect to Perl 5.8.
+.  PCRE does not have full UTF-8 support. Details 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,
+        (?!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-
+        tions are counted, but their entries in the offsets  vector  are  never
+        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
+        branch.
+. 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,
+        \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
+        are encountered by PCRE, an error is generated.
+. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
+        is  built  with Unicode character property support. The properties that
+        can be tested with \p and \P are limited to the general category  prop-
+        erties such as Lu and Nd.
+. PCRE does support the \Q...\E escape for quoting substrings. Charac-
+        ters in between are treated as literals.  This  is  slightly  different
+        from  Perl  in  that  $  and  @ are also handled as literals inside the
+        quotes. In Perl, they cause variable interpolation (but of course  PCRE
+        does not have variables). Note the following examples:
+            Pattern            PCRE matches      Perl matches
+            \Qabc$xyz\E        abc$xyz           abc followed by the
+                                                   contents of $xyz
+            \Qabc\$xyz\E       abc\$xyz          abc\$xyz
+            \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
+        The  \Q...\E  sequence  is recognized both inside and outside character
+        classes.
+. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})
+        constructions.  However,  there is support for recursive patterns using
+        the non-Perl items (?R),  (?number),  and  (?P>name).  Also,  the  PCRE
+        "callout"  feature allows an external function to be called during pat-
+        tern matching. See the pcrecallout documentation for details.
+. There are some differences that are concerned with the  settings  of
+        captured  strings  when  part  of  a  pattern is repeated. For example,
+        matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
+        unset, but in PCRE it is set to "b".
+. PCRE provides some extensions to the Perl regular expression facil-
+        ities:
+        (a) Although lookbehind assertions 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  $
+        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.
+        (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-
+        TURE options for pcre_exec() have no Perl equivalents.
+        (g) The (?R), (?number), and (?P>name) constructs allows for  recursive
+        pattern  matching  (Perl  can  do  this using the (?p{code}) construct,
+        which PCRE cannot support.)
+        (h) PCRE supports named capturing substrings, using the Python  syntax.
+        (i)  PCRE  supports  the  possessive quantifier "++" syntax, taken from
+        Sun's Java package.
+        (j) The (R) condition, for testing recursion, is a PCRE extension.
+        (k) The callout facility is PCRE-specific.
+        (l) The partial matching facility is PCRE-specific.
+        (m) Patterns compiled by PCRE can be saved and re-used at a later time,
+        even on different hosts that have the other endianness.
+ Last updated: 09 September 2004
+ Copyright (c) 1997-2004 University of Cambridge.
+ -----------------------------------------------------------------------------
+ PCRE(3)                                                                PCRE(3)
+ NAME
+        PCRE - Perl-compatible regular expressions
+ PCRE REGULAR EXPRESSION DETAILS
+        The  syntax  and semantics of the regular expressions supported by PCRE
+        are described below. Regular expressions are also described in the Perl
+        documentation  and  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 descrip-
+        tion 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
+        pcre_compile()  with  the  PCRE_UTF8  option.  How this 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.
+        A regular expression is a pattern that is  matched  against  a  subject
+        string  from  left  to right. Most characters stand for themselves in a
+        pattern, and match the corresponding characters in the  subject.  As  a
+        trivial example, the pattern
+          The quick brown fox
+        matches  a portion of a subject string that is identical to itself. The
+        power of regular expressions comes from the ability to include alterna-
+        tives  and repetitions in the pattern. These are encoded in the pattern
+        by the use of metacharacters, which do not  stand  for  themselves  but
+        instead are interpreted in some special way.
+        There  are  two different sets of metacharacters: those that are recog-
+        nized anywhere in the pattern except within square brackets, and  those
+        that  are  recognized  in square brackets. Outside square brackets, the
+        metacharacters are as follows:
+          \      general escape character with several uses
+          ^      assert start of string (or line, in multiline mode)
+          $      assert end of string (or line, in multiline mode)
+          .      match any character except newline (by default)
+          [      start character class definition
+          |      start of alternative branch
+          (      start subpattern
+          )      end subpattern
+          ?      extends the meaning of (
+                 also 0 or 1 quantifier
+                 also quantifier minimizer
+          *      0 or more quantifier
+          +      1 or more quantifier
+                 also "possessive quantifier"
+          {      start min/max quantifier
+        Part of a pattern that is in square brackets  is  called  a  "character
+        class". In a character class the only metacharacters are:
+          \      general escape character
+          ^      negate the class, but only if the first character
+          -      indicates character range
+          [      POSIX character class (only if followed by POSIX
+                   syntax)
+          ]      terminates the character class
+        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-alphameric character, it takes away any
-      special  meaning  that  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 pattern. This applies whether or not the follow-
-      ing character would otherwise  be  interpreted  as  a  meta-
-      character,  so it is always safe to precede a non-alphameric
-      with "\" to specify that it stands for itself.  In  particu-
-      lar, if you want to match a backslash, you write "\\".
-      If a pattern is compiled with the PCRE_EXTENDED option, whi-
-      tespace in the pattern (other than in a character class) and
-      characters between a "#" outside a character class  and  the
-      next  newline  character  are ignored. An escaping backslash
-      can be used to include a whitespace or "#" character as part
-      of the pattern.
-      A second use of backslash provides a way  of  encoding  non-
-      printing  characters  in patterns in a visible manner. There
-      is no restriction on the appearance of non-printing  charac-
-      ters,  apart from the binary zero that terminates a pattern,
-      but when a pattern is being prepared by text editing, it  is
-      usually  easier to use one of the following escape sequences
-      than the binary character it represents:
-        \a     alarm, that is, the BEL character (hex 07)
-        \cx    "control-x", where x is any character
-        \e     escape (hex 1B)
-        \f     formfeed (hex 0C)
-        \n     newline (hex 0A)
-        \r     carriage return (hex 0D)
-        \t     tab (hex 09)
-        \xhh   character with hex code hh
-        \ddd   character with octal code ddd, or backreference
-      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 inverted.  Thus "\cz" becomes  hex
-A, but "\c{" becomes hex 3B, while "\c;" becomes hex 7B.
-      After "\x", up to two hexadecimal digits are  read  (letters
-      can be in upper or lower case).
-      After "\0" up to two further octal digits are read. In  both
-      cases,  if  there are fewer 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.  Make sure you
-      supply two digits after the initial zero  if  the  character
-      that follows is itself an octal digit.
-      The handling of a backslash followed by a digit other than 0
-      is  complicated.   Outside  a character class, PCRE reads it
-      and any following digits 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 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 and there have not been that many capturing
-      subpatterns, PCRE re-reads up to three octal digits  follow-
-      ing  the  backslash,  and  generates  a single byte from the
-      least significant 8 bits of the value. Any subsequent digits
-      stand for themselves.  For example:
-        \040   is another way of writing a space
-        \40    is the same, provided there are fewer than 40
-                  previous capturing subpatterns
-        \7     is always a back reference
-        \11    might be a back reference, or another way of
-                  writing a tab
-        \011   is always a tab
-        \0113  is a tab followed by the character "3"
-        \113   is the character with octal code 113 (since there
-                  can be no more than 99 back references)
-        \377   is a byte consisting entirely of 1 bits
-        \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  intro-
-      duced  by  a  leading zero, because no more than three octal
-      digits are ever read.
-      All the sequences that define a single  byte  value  can  be
-      used both inside and outside character classes. In addition,
-      inside a character class, the sequence "\b"  is  interpreted
-      as  the  backspace  character  (hex 08). Outside a character
-      class it has a different meaning (see below).
-      The third use of backslash is for specifying generic charac-
-      ter types:
-        \d     any decimal digit
-        \D     any character that is not a decimal digit
-        \s     any whitespace character
-        \S     any character that is not a whitespace character
-        \w     any "word" character
-        \W     any "non-word" character
-      Each pair of escape sequences partitions the complete set of
-      characters  into  two  disjoint  sets.  Any  given character
-      matches one, and only one, of each pair.
-      A "word" character is any letter or digit or the  underscore
-      character,  that  is,  any  character which can be part of a
-      Perl "word". The definition of letters and  digits  is  con-
-      trolled  by PCRE's character tables, and may vary if locale-
-      specific matching is  taking  place  (see  "Locale  support"
-      above). For example, in the "fr" (French) locale, some char-
-      acter codes greater than 128 are used for accented  letters,
-      and these are matched by \w.
-      These character type sequences can appear  both  inside  and
-      outside  character classes. They each match one character of
-      the appropriate type. If the current matching  point  is  at
-      the end of the subject string, all of them fail, since there
-      is no character to match.
-      The fourth use of backslash is  for  certain  simple  asser-
-      tions. An assertion specifies a condition that has to be met
-      at a particular point in  a  match,  without  consuming  any
-      characters  from  the subject string. The use of subpatterns
-      for more complicated  assertions  is  described  below.  The
-      backslashed assertions are
-        \b     word boundary
-        \B     not a word boundary
-        \A     start of subject (independent of multiline mode)
-        \Z     end of subject or newline at  end  (independent  of
-      multiline mode)
-        \z     end of subject (independent of multiline mode)
-      These assertions may not appear in  character  classes  (but
-      note that "\b" has a different meaning, namely the backspace
-      character, inside a character class).
-      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. 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.
-      The \A, \Z, and \z assertions differ  from  the  traditional
-      circumflex  and  dollar  (described below) in that they only
-      ever match at the very start and end of the subject  string,
-      whatever  options  are  set.  They  are  not affected by the
-      PCRE_NOTBOL or PCRE_NOTEOL options. If the startoffset argu-
-      ment  of  pcre_exec()  is  non-zero, \A can never match. The
-      difference between \Z and \z is that  \Z  matches  before  a
-      newline  that is the last character of the string as well as
-      at the end of the string, whereas \z  matches  only  at  the
-      end.
+        The backslash character has several uses. Firstly, if it is followed by
+        a  non-alphanumeric  character,  it takes away any special meaning that
+        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
+        pattern.  This escaping action applies whether  or  not  the  following
+        character  would  otherwise be interpreted as a metacharacter, so it is
+        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-
+        slash, you write \\.
+        If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
+        the  pattern (other than in a character class) and characters between a
+        # outside a character class and the next newline character are ignored.
+        An  escaping backslash can be used to include a whitespace or # charac-
+        ter as part of the pattern.
+        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-
+        ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
+        sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
+        tion. Note the following examples:
+          Pattern            PCRE matches   Perl matches
+          \Qabc$xyz\E        abc$xyz        abc followed by the
+                                              contents of $xyz
+          \Qabc\$xyz\E       abc\$xyz       abc\$xyz
+          \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
+        The \Q...\E sequence is recognized both inside  and  outside  character
+        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
+        appearance  of non-printing characters, apart from the binary zero that
+        terminates a pattern, but when a pattern  is  being  prepared  by  text
+        editing,  it  is  usually  easier  to  use  one of the following escape
+        sequences than the binary character it represents:
+          \a        alarm, that is, the BEL character (hex 07)
+          \cx       "control-x", where x is any character
+          \e        escape (hex 1B)
+          \f        formfeed (hex 0C)
+          \n        newline (hex 0A)
+          \r        carriage return (hex 0D)
+          \t        tab (hex 09)
+          \ddd      character with octal code ddd, or backreference
+          \xhh      character with hex code hh
+          \x{hhh..} character with hex code hhh... (UTF-8 mode only)
+        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
+        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
+        in upper or lower case). In UTF-8 mode, any number of hexadecimal  dig-
+        its  may  appear between \x{ and }, but the value of the character code
+        must be less than 2**31 (that is,  the  maximum  hexadecimal  value  is
+FFFFFFF).  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 hex-
+        adecimal 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 when PCRE is in UTF-8 mode. There is no  difference
+        in  the  way they are handled. For example, \xdc is exactly the same as
+        \x{dc}.
+        After \0 up to two further octal digits are read.  In  both  cases,  if
+        there  are fewer 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 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
+        have been at least that many previous capturing left parentheses in the
+        expression,  the  entire  sequence  is  taken  as  a  back reference. A
+        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
+        and there have not been that many capturing subpatterns, PCRE  re-reads
+        up  to three octal digits following the backslash, and generates a sin-
+        gle byte from the least significant 8 bits of the value. Any subsequent
+        digits stand for themselves.  For example:
+          \040   is another way of writing a space
+          \40    is the same, provided there are fewer than 40
+                    previous capturing subpatterns
+          \7     is always a back reference
+          \11    might be a back reference, or another way of
+                    writing a tab
+          \011   is always a tab
+          \0113  is a tab followed by the character "3"
+          \113   might be a back reference, otherwise the
+                    character with octal code 113
+          \377   might be a back reference, otherwise
+                    the byte consisting entirely of 1 bits
+          \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
+        leading zero, because no more than three octal digits are ever read.
+        All the sequences that define a single byte value  or  a  single  UTF-8
+        character (in UTF-8 mode) can be used both inside and outside character
+        classes. In addition, inside a character  class,  the  sequence  \b  is
+        interpreted as the backspace character (hex 08), and the sequence \X is
+        interpreted as the character "X".  Outside  a  character  class,  these
+        sequences have different meanings (see below).
+    Generic character types
+        The  third  use of backslash is for specifying generic character types.
+        The following are always recognized:
+          \d     any decimal digit
+          \D     any character that is not a decimal digit
+          \s     any whitespace character
+          \S     any character that is not a whitespace character
+          \w     any "word" character
+          \W     any "non-word" character
+        Each pair of escape sequences partitions the complete set of characters
+        into  two disjoint sets. Any given character matches one, and only one,
+        of each pair.
+        These character type sequences can appear both inside and outside char-
+        acter  classes.  They each match one character of the appropriate type.
+        If the current matching point is at the end of the subject string,  all
+        of them fail, since there is no character to match.
+        For  compatibility  with Perl, \s does not match the VT character (code
+).  This makes it different from the the POSIX "space" class. The  \s
+        characters are HT (9), LF (10), FF (12), CR (13), and space (32).
+        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-
+        trolled  by PCRE's low-valued character tables, and may vary if locale-
+        specific matching is taking place (see "Locale support" in the  pcreapi
+        page).  For  example,  in  the  "fr_FR" (French) locale, some character
+        codes greater than 128 are used for accented  letters,  and  these  are
+        matched by \w.
+        In  UTF-8 mode, characters with values greater than 128 never match \d,
+        \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
+        code character property support is available.
+    Unicode character properties
+        When PCRE is built with Unicode character property support, three addi-
+        tional escape sequences to match generic character types are  available
+        when UTF-8 mode is selected. They 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
+        general category properties. Each character has exactly one such  prop-
+        erty,  specified  by  a two-letter abbreviation. For compatibility with
+        Perl, negation can be 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
+        properties that start with that letter. In this case, in the absence of
+        negation, the curly brackets in the escape sequence are optional; these
+        two examples have the same effect:
+          \p{L}
+          \pL
+        The following property codes are supported:
+          C     Other
+          Cc    Control
+          Cf    Format
+          Cn    Unassigned
+          Co    Private use
+          Cs    Surrogate
+          L     Letter
+          Ll    Lower case letter
+          Lm    Modifier letter
+          Lo    Other letter
+          Lt    Title case letter
+          Lu    Upper case letter
+          M     Mark
+          Mc    Spacing mark
+          Me    Enclosing mark
+          Mn    Non-spacing mark
+          N     Number
+          Nd    Decimal number
+          Nl    Letter number
+          No    Other number
+          P     Punctuation
+          Pc    Connector punctuation
+          Pd    Dash punctuation
+          Pe    Close punctuation
+          Pf    Final punctuation
+          Pi    Initial punctuation
+          Po    Other punctuation
+          Ps    Open punctuation
+          S     Symbol
+          Sc    Currency symbol
+          Sk    Modifier symbol
+          Sm    Mathematical symbol
+          So    Other symbol
+          Z     Separator
+          Zl    Line separator
+          Zp    Paragraph separator
+          Zs    Space separator
+        Extended  properties such as "Greek" or "InMusicalSymbols" are not sup-
+        ported by PCRE.
+        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
+        extended Unicode sequence. \X is equivalent to
+          (?>\PM\pM*)
+        That is, it matches a character without the "mark"  property,  followed
+        by  zero  or  more  characters with the "mark" property, and treats the
+        sequence as an atomic group (see below).  Characters  with  the  "mark"
+        property are typically accents that affect the preceding character.
+        Matching  characters  by Unicode property is not fast, because PCRE has
+        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.
+    Simple assertions
+        The fourth use of backslash is for certain simple assertions. An asser-
+        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
+        use  of subpatterns for more complicated assertions is described below.
+        The backslashed assertions are:
+          \b     matches at a word boundary
+          \B     matches when not at a word boundary
+          \A     matches at start of subject
+          \Z     matches at end of subject or before newline at end
+          \z     matches at end of subject
+          \G     matches at first matching position in subject
+        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
+        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
+        string if the first or last character matches \w, respectively.
+        The  \A,  \Z,  and \z assertions differ from the traditional circumflex
+        and dollar (described in the next section) in that they only ever match
+        at  the  very start and end of the subject string, whatever options are
+        set. Thus, they are independent of multiline mode. These  three  asser-
+        tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
+        affect only the behaviour of the circumflex and dollar  metacharacters.
+        However,  if the startoffset argument of pcre_exec() is non-zero, indi-
+        cating that matching is to start at a point other than the beginning of
+        the  subject,  \A  can never match. The difference between \Z and \z is
+        that \Z matches before a newline that is  the  last  character  of  the
+        string  as well as at the end of the string, whereas \z matches only at
+        the end.
+        The \G assertion is true only when the current matching position is  at
+        the  start point of the match, as specified by the startoffset argument
+        of pcre_exec(). It differs from \A when the  value  of  startoffset  is
+        non-zero.  By calling pcre_exec() multiple times with appropriate argu-
+        ments, you can mimic Perl's /g option, and it is in this kind of imple-
+        mentation where \G can be useful.
+        Note,  however,  that  PCRE's interpretation of \G, as the start of the
+        current match, is subtly different from Perl's, which defines it as the
+        end  of  the  previous  match. In Perl, these can be different when the
+        previously matched string was empty. Because PCRE does just  one  match
+        at a time, it cannot reproduce this behaviour.
+        If  all  the alternatives of a pattern begin with \G, the expression is
+        anchored to the starting match position, and the "anchored" flag is set
+        in the compiled regular expression.
  CIRCUMFLEX AND DOLLAR
-      Outside a character class, in the default matching mode, the
-      circumflex  character  is an assertion which is true only if
-      the current matching point is at the start  of  the  subject
-      string.  If  the startoffset argument of pcre_exec() is non-
-      zero, circumflex can never match. Inside a character  class,
-      circumflex has an entirely different meaning (see below).
-      Circumflex need not be the first character of the pattern if
-      a  number of alternatives are involved, but it should be the
-      first thing in each alternative in which it appears  if  the
-      pattern is ever to match that branch. If all possible alter-
-      natives start with a circumflex, that is, if the pattern  is
-      constrained to match only at the start of the subject, it is
-      said to be an "anchored" pattern. (There are also other con-
-      structs that can cause a pattern to be anchored.)
-      A dollar character is an assertion which is true only if the
-      current  matching point is at the end of the subject string,
-      or immediately before a newline character that is  the  last
-      character in the string (by default). Dollar need not be the
-      last character of the pattern if a  number  of  alternatives
-      are  involved,  but it should be the last item in any branch
-      in which it appears.  Dollar has no  special  meaning  in  a
-      character class.
-      The meaning of dollar can be changed so that it matches only
-      at   the   very   end   of   the   string,  by  setting  the
-      PCRE_DOLLAR_ENDONLY option at compile or matching time. This
-      does not affect the \Z assertion.
-      The meanings of the circumflex  and  dollar  characters  are
-      changed  if  the  PCRE_MULTILINE option is set. When this is
-      the case,  they  match  immediately  after  and  immediately
-      before an internal "\n" character, respectively, in addition
-      to matching at the start and end of the subject string.  For
-      example,  the  pattern  /^abc$/  matches  the subject string
-      "def\nabc" in multiline  mode,  but  not  otherwise.  Conse-
-      quently,  patterns  that  are  anchored  in single line mode
-      because all branches start with "^" are not anchored in mul-
-      tiline mode, and a match for circumflex is possible when the
-      startoffset  argument  of  pcre_exec()  is   non-zero.   The
-      PCRE_DOLLAR_ENDONLY  option  is ignored if PCRE_MULTILINE is
-      set.
-      Note that the sequences \A, \Z, and \z can be used to  match
-      the  start  and end of the subject in both modes, and if all
-      branches of a pattern start with \A is it  always  anchored,
-      whether PCRE_MULTILINE is set or not.
+        Outside a character class, in the default matching mode, the circumflex
+        character is an assertion that is true only  if  the  current  matching
+        point  is  at the start of the subject string. If the startoffset argu-
+        ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the
+        PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
+        has an entirely different meaning (see below).
+        Circumflex need not be the first character of the pattern if  a  number
+        of  alternatives are involved, but it should be the first thing in each
+        alternative in which it appears if the pattern is ever  to  match  that
+        branch.  If all possible alternatives start with a circumflex, that is,
+        if the pattern is constrained to match only at the start  of  the  sub-
+        ject,  it  is  said  to be an "anchored" pattern. (There are also other
+        constructs that can cause a pattern to be anchored.)
+        A dollar character is an assertion that is true  only  if  the  current
+        matching  point  is  at  the  end of the subject string, or immediately
+        before a newline character that is the last character in the string (by
+        default).  Dollar  need  not  be the last character of the pattern if a
+        number of alternatives are involved, but it should be the last item  in
+        any  branch  in  which  it appears.  Dollar has no special meaning in a
+        character class.
+        The meaning of dollar can be changed so that it  matches  only  at  the
+        very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at
+        compile time. This does not affect the \Z assertion.
+        The meanings of the circumflex and dollar characters are changed if the
+        PCRE_MULTILINE option is set. When this is the case, they match immedi-
+        ately after and  immediately  before  an  internal  newline  character,
+        respectively,  in addition to matching at the start and end of the sub-
+        ject string. For example,  the  pattern  /^abc$/  matches  the  subject
+        string  "def\nabc"  (where \n represents a newline character) in multi-
+        line mode, but not otherwise.  Consequently, patterns that are anchored
+        in  single line mode because all branches start with ^ are not anchored
+        in multiline mode, and a match for  circumflex  is  possible  when  the
+        startoffset   argument   of  pcre_exec()  is  non-zero.  The  PCRE_DOL-
+        LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
+        Note that the sequences \A, \Z, and \z can be used to match  the  start
+        and  end of the subject in both modes, and if all branches of a pattern
+        start with \A it is always anchored, whether PCRE_MULTILINE is  set  or
+        not.
  FULL STOP (PERIOD, DOT)
-      Outside a character class, a dot in the pattern matches  any
-      one character in the subject, including a non-printing char-
-      acter, but not (by default)  newline.   If  the  PCRE_DOTALL
-      option  is set, dots match newlines as well. The handling of
-      dot is entirely independent of the  handling  of  circumflex
-      and  dollar,  the  only  relationship  being  that they both
-      involve newline characters. Dot has no special meaning in  a
-      character class.
- SQUARE BRACKETS
-      An opening square bracket introduces a character class, ter-
-      minated  by  a  closing  square  bracket.  A  closing square
-      bracket on its own is  not  special.  If  a  closing  square
-      bracket  is  required as a member of the class, it should be
-      the first data character in the class (after an initial cir-
-      cumflex, if present) or escaped with a backslash.
-      A character class matches a single character in the subject;
-      the  character  must  be in the set of characters defined by
-      the class, unless the first character in the class is a cir-
-      cumflex,  in which case the subject character must not be in
-      the set defined by the class. If a  circumflex  is  actually
-      required  as  a  member  of  the class, ensure it is not the
-      first character, or escape it with a backslash.
-      For example, the character class [aeiou] matches  any  lower
-      case vowel, while [^aeiou] matches any character that is not
-      a lower case vowel. Note that a circumflex is  just  a  con-
-      venient  notation for specifying the characters which are in
-      the class by enumerating those that are not. It  is  not  an
-      assertion:  it  still  consumes a character from the subject
-      string, and fails if the current pointer is at  the  end  of
-      the string.
-      When caseless matching  is  set,  any  letters  in  a  class
-      represent  both their upper case and lower case versions, so
-      for example, a caseless [aeiou] matches "A" as well as  "a",
-      and  a caseless [^aeiou] does not match "A", whereas a case-
-      ful version would.
-      The newline character is never treated in any special way in
-      character  classes,  whatever the setting of the PCRE_DOTALL
-      or PCRE_MULTILINE options is. A  class  such  as  [^a]  will
-      always match a newline.
-      The minus (hyphen) character can be used to specify a  range
-      of  characters  in  a  character  class.  For example, [d-m]
-      matches any letter between d and m, inclusive.  If  a  minus
-      character  is required in a class, it must be escaped with a
-      backslash or appear in a position where it cannot be  inter-
-      preted as indicating a range, typically as the first or last
-      character in the class.
-      It is not possible to have the literal character "]" as  the
-      end  character  of  a  range.  A  pattern such as [W-]46] is
-      interpreted as a class of two characters ("W" and "-")  fol-
-      lowed by a literal string "46]", so it would match "W46]" or
-      "-46]". However, if the "]" is escaped with a  backslash  it
-      is  interpreted  as  the end of range, so [W-\]46] is inter-
-      preted as a single class containing a range followed by  two
-      separate characters. The octal or hexadecimal representation
-      of "]" can also be used to end a range.
-      Ranges operate in ASCII collating sequence. They can also be
-      used  for  characters  specified  numerically,  for  example
-      [\000-\037]. If a range that includes letters is  used  when
-      caseless  matching  is set, it matches the letters in either
-      case. For example, [W-c] is equivalent  to  [][\^_`wxyzabc],
-      matched  caselessly,  and  if  character tables for the "fr"
-      locale are in use, [\xc8-\xcb] matches accented E characters
-      in both cases.
-      The character types \d, \D, \s, \S,  \w,  and  \W  may  also
-      appear  in  a  character  class, and add the characters that
-      they match to the class. For example, [\dABCDEF] matches any
-      hexadecimal  digit.  A  circumflex  can conveniently be used
-      with the upper case character types to specify a  more  res-
-      tricted set of characters than the matching lower case type.
-      For example, the class [^\W_] matches any letter  or  digit,
-      but not underscore.
-      All non-alphameric characters other than \,  -,  ^  (at  the
-      start)  and  the  terminating ] are non-special in character
-      classes, but it does no harm if they are escaped.
+        Outside a character class, a dot in the pattern matches any one charac-
+        ter in the subject, including a non-printing  character,  but  not  (by
+        default)  newline.   In  UTF-8 mode, a dot matches any UTF-8 character,
+        which might be more than one byte long, except (by default) newline. If
+        the  PCRE_DOTALL  option  is set, dots match newlines as well. The han-
+        dling of dot is entirely independent of the handling of circumflex  and
+        dollar,  the  only  relationship  being  that they both involve newline
+        characters. Dot has no special meaning in a character class.
+ MATCHING A SINGLE BYTE
+        Outside a character class, the escape sequence \C matches any one byte,
+        both  in  and  out of UTF-8 mode. Unlike a dot, it can match a newline.
+        The feature is provided in Perl in order to match individual  bytes  in
+        UTF-8  mode.  Because  it  breaks  up  UTF-8 characters into individual
+        bytes, what remains in the string may be a malformed UTF-8 string.  For
+        this reason, the \C escape sequence is best avoided.
+        PCRE  does  not  allow \C to appear in lookbehind assertions (described
+        below), because in UTF-8 mode this would make it impossible  to  calcu-
+        late the length of the lookbehind.
+ 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,
+        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
+        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
+        circumflex is actually required as a member of the class, ensure it  is
+        not the first character, or escape it with a backslash.
+        For  example, the character class [aeiou] matches any lower case vowel,
+        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-
+        sumes a character from the subject string, and therefore  it  fails  if
+        the current pointer is at the end of the string.
+        In  UTF-8 mode, characters with values greater than 255 can be included
+        in a class as a literal string of bytes, or by using the  \x{  escaping
+        mechanism.
+        When  caseless  matching  is set, any letters in a class represent both
+        their upper case and lower case versions, so for  example,  a  caseless
+        [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not
+        match "A", whereas a caseful version would. When running in UTF-8 mode,
+        PCRE  supports  the  concept of case for characters with values greater
+        than 128 only when it is compiled with Unicode property support.
+        The newline character is never treated in any special way in  character
+        classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE
+        options is. A class such as [^a] will always match a newline.
+        The minus (hyphen) character can be used to specify a range of  charac-
+        ters  in  a  character  class.  For  example,  [d-m] matches any letter
+        between d and m, inclusive. If a  minus  character  is  required  in  a
+        class,  it  must  be  escaped  with a backslash or appear in a position
+        where it cannot be interpreted as indicating a range, typically as  the
+        first or last character in the class.
+        It is not possible to have the literal character "]" as the end charac-
+        ter of a range. A pattern such as [W-]46] is interpreted as a class  of
+        two  characters ("W" and "-") followed by a literal string "46]", so it
+        would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a
+        backslash  it is interpreted as the end of range, so [W-\]46] is inter-
+        preted as a class containing a range followed by two other  characters.
+        The  octal or hexadecimal representation of "]" can also be used to end
+        a range.
+        Ranges operate in the collating sequence of character values. They  can
+        also   be  used  for  characters  specified  numerically,  for  example
+        [\000-\037]. In UTF-8 mode, ranges can include characters whose  values
+        are greater than 255, for example [\x{100}-\x{2ff}].
+        If a range that includes letters is used when caseless matching is set,
+        it matches the letters in either case. For example, [W-c] is equivalent
+        to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if
+        character tables for the "fr_FR" locale are in use, [\xc8-\xcb] matches
+        accented  E  characters in both cases. In UTF-8 mode, PCRE supports the
+        concept of case for characters with values greater than 128  only  when
+        it is compiled with Unicode property support.
+        The  character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear
+        in a character class, and add the characters that  they  match  to  the
+        class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
+        flex can conveniently be used with the upper case  character  types  to
+        specify  a  more  restricted  set of characters than the matching lower
+        case type. For example, the class [^\W_] matches any letter  or  digit,
+        but not underscore.
+        The  only  metacharacters  that are recognized in character classes are
+        backslash, hyphen (only where it can be  interpreted  as  specifying  a
+        range),  circumflex  (only  at the start), opening square bracket (only
+        when it can be interpreted as introducing a POSIX class name - see  the
+        next  section),  and  the  terminating closing square bracket. However,
+        escaping other non-alphanumeric characters does no harm.
  POSIX CHARACTER CLASSES
-      Perl 5.6 (not yet released at the time of writing) is  going
-      to  support  the POSIX notation for character classes, which
-      uses names enclosed by  [:  and  :]   within  the  enclosing
-      square brackets. PCRE supports this notation. For example,
-        [01[:alpha:]%]
-      matches "0", "1", any alphabetic character, or "%". The sup-
-      ported class names are
-        alnum    letters and digits
-        alpha    letters
-        ascii    character codes 0 - 127
-        cntrl    control characters
-        digit    decimal digits (same as \d)
-        graph    printing characters, excluding space
-        lower    lower case letters
-        print    printing characters, including space
-        punct    printing characters, excluding letters and digits
-        space    white space (same as \s)
-        upper    upper case letters
-        word     "word" characters (same as \w)
-        xdigit   hexadecimal digits
-      The names "ascii" and "word" are  Perl  extensions.  Another
-      Perl  extension is negation, which is indicated by a ^ char-
-      acter after the colon. For example,
-        [12[:^digit:]]
-      matches "1", "2", or any non-digit.  PCRE  (and  Perl)  also
-      recogize  the POSIX syntax [.ch.] and [=ch=] where "ch" is a
-      "collating element", but these are  not  supported,  and  an
-      error is given if they are encountered.
+        Perl supports the POSIX notation for character classes. This uses names
+        enclosed  by  [: and :] within the enclosing square brackets. PCRE also
+        supports this notation. For example,
+          [01[:alpha:]%]
+        matches "0", "1", any alphabetic character, or "%". The supported class
+        names are
+          alnum    letters and digits
+          alpha    letters
+          ascii    character codes 0 - 127
+          blank    space or tab only
+          cntrl    control characters
+          digit    decimal digits (same as \d)
+          graph    printing characters, excluding space
+          lower    lower case letters
+          print    printing characters, including space
+          punct    printing characters, excluding letters and digits
+          space    white space (not quite the same as \s)
+          upper    upper case letters
+          word     "word" characters (same as \w)
+          xdigit   hexadecimal digits
+        The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
+        and space (32). Notice that this list includes the VT  character  (code
+). This makes "space" different to \s, which does not include VT (for
+        Perl compatibility).
+        The name "word" is a Perl extension, and "blank"  is  a  GNU  extension
+        from  Perl  5.8. Another Perl extension is negation, which is indicated
+        by a ^ character after the colon. For example,
+          [12[:^digit:]]
+        matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the
+        POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
+        these are not supported, and an error is given if they are encountered.
+        In UTF-8 mode, characters with values greater than 128 do not match any
+        of the POSIX character classes.
  VERTICAL BAR
-      Vertical bar characters are  used  to  separate  alternative
-      patterns. For example, the pattern
-        gilbert|sullivan
+        Vertical bar characters are used to separate alternative patterns.  For
+        example, the pattern
-      matches either "gilbert" or "sullivan". Any number of alter-
+          gilbert|sullivan
-      natives  may  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 are within  a
-      subpattern  (defined  below),  "succeeds" means matching the
-      rest of the main pattern as well as the alternative  in  the
-      subpattern.
+        matches  either "gilbert" or "sullivan". Any number of alternatives may
+        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 alterna-
+        tives  are within a subpattern (defined below), "succeeds" means match-
+        ing the rest of the main pattern as well as the alternative in the sub-
+        pattern.
  INTERNAL OPTION SETTING
-      The settings of PCRE_CASELESS, PCRE_MULTILINE,  PCRE_DOTALL,
-      and  PCRE_EXTENDED can be changed from within the pattern by
-      a sequence of Perl option letters enclosed between "(?"  and
-      ")". The option letters are
-        i  for PCRE_CASELESS
-        m  for PCRE_MULTILINE
-        s  for PCRE_DOTALL
-        x  for PCRE_EXTENDED
-      For example, (?im) sets caseless, multiline matching. It  is
-      also possible to unset these options by preceding the letter
-      with a hyphen, and a combined setting and unsetting such  as
-      (?im-sx),  which sets PCRE_CASELESS and PCRE_MULTILINE while
-      unsetting PCRE_DOTALL and PCRE_EXTENDED, is also  permitted.
-      If  a  letter  appears both before and after the hyphen, the
-      option is unset.
-      The scope of these option changes depends on  where  in  the
-      pattern  the  setting  occurs. For settings that are outside
-      any subpattern (defined below), the effect is the same as if
-      the  options were set or unset at the start of matching. The
-      following patterns all behave in exactly the same way:
-        (?i)abc
-        a(?i)bc
-        ab(?i)c
-        abc(?i)
-      which in turn is the same as compiling the pattern abc  with
-      PCRE_CASELESS  set.   In  other words, such "top level" set-
-      tings apply to the whole pattern  (unless  there  are  other
-      changes  inside subpatterns). If there is more than one set-
-      ting of the same option at top level, the rightmost  setting
-      is used.
-      If an option change occurs inside a subpattern,  the  effect
-      is  different.  This is a change of behaviour in Perl 5.005.
-      An option change inside a subpattern affects only that  part
-      of the subpattern that follows it, so
-        (a(?i)b)c
-      matches  abc  and  aBc  and  no  other   strings   (assuming
-      PCRE_CASELESS  is  not used).  By this means, options can be
-      made to have different settings in different  parts  of  the
-      pattern.  Any  changes  made  in one alternative do carry on
-      into subsequent branches within  the  same  subpattern.  For
-      example,
-        (a(?i)b|c)
-      matches "ab", "aB", "c", and "C", even though when  matching
-      "C" the first branch is abandoned before the option setting.
-      This is because the effects of  option  settings  happen  at
-      compile  time. There would be some very weird behaviour oth-
-      erwise.
-      The PCRE-specific options PCRE_UNGREEDY and  PCRE_EXTRA  can
-      be changed in the same way as the Perl-compatible options by
-      using the characters U and X  respectively.  The  (?X)  flag
-      setting  is  special in that it must always occur earlier in
-      the pattern than any of the additional features it turns on,
-      even when it is at top level. It is best put at the start.
+        The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
+        PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a
+        sequence  of  Perl  option  letters  enclosed between "(?" and ")". The
+        option letters are
+          i  for PCRE_CASELESS
+          m  for PCRE_MULTILINE
+          s  for PCRE_DOTALL
+          x  for PCRE_EXTENDED
+        For example, (?im) sets caseless, multiline matching. It is also possi-
+        ble to unset these options by preceding the letter with a hyphen, and a
+        combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-
+        LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,
+        is also permitted. If a  letter  appears  both  before  and  after  the
+        hyphen, the option is unset.
+        When  an option change occurs at top level (that is, not inside subpat-
+        tern parentheses), the change applies to the remainder of  the  pattern
+        that follows.  If the change is placed right at the start of a pattern,
+        PCRE extracts it into the global options (and it will therefore show up
+        in data extracted by the pcre_fullinfo() function).
+        An option change within a subpattern affects only that part of the cur-
+        rent pattern that follows it, so
+          (a(?i)b)c
+        matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
+        used).   By  this means, options can be made to have different settings
+        in different parts of the pattern. Any changes made in one  alternative
+        do  carry  on  into subsequent branches within the same subpattern. For
+        example,
+          (a(?i)b|c)
+        matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
+        first  branch  is  abandoned before the option setting. This is because
+        the effects of option settings happen at compile time. There  would  be
+        some very weird behaviour otherwise.
+        The  PCRE-specific  options PCRE_UNGREEDY and PCRE_EXTRA can be changed
+        in the same way as the Perl-compatible options by using the  characters
+        U  and X respectively. The (?X) flag setting is special in that it must
+        always occur earlier in the pattern than any of the additional features
+        it  turns on, even when it is at top level. It is best to put it at the
+        start.
  SUBPATTERNS
-      Subpatterns are delimited by parentheses  (round  brackets),
-      which can be nested.  Marking part of a pattern as a subpat-
-      tern does two things:
-. It localizes a set of alternatives. For example, the pat-
-      tern
-        cat(aract|erpillar|)
-      matches one of the words "cat",  "cataract",  or  "caterpil-
-      lar".  Without  the  parentheses, it would match "cataract",
-      "erpillar" or the empty string.
-. It sets up the subpattern as a capturing  subpattern  (as
-      defined  above).   When the whole pattern matches, that por-
-      tion of the subject string that matched  the  subpattern  is
-      passed  back  to  the  caller  via  the  ovector argument of
-      pcre_exec(). Opening parentheses are counted  from  left  to
-      right (starting from 1) to obtain the numbers of the captur-
-      ing subpatterns.
-      For example, if the string "the red king" is matched against
-      the pattern
-        the ((red|white) (king|queen))
-      the captured substrings are "red king", "red",  and  "king",
-      and are numbered 1, 2, and 3.
-      The fact that plain parentheses fulfil two functions is  not
-      always  helpful.  There are often times when a grouping sub-
-      pattern is required without a capturing requirement.  If  an
-      opening parenthesis is followed by "?:", the subpattern does
-      not do any capturing, and is not counted when computing  the
-      number of any subsequent capturing subpatterns. For example,
-      if the string "the white queen" is matched against the  pat-
-      tern
-        the ((?:red|white) (king|queen))
-      the captured substrings are "white queen" and  "queen",  and
-      are  numbered  1  and 2. The maximum number of captured sub-
-      strings is 99, and the maximum number  of  all  subpatterns,
-      both capturing and non-capturing, is 200.
-      As a  convenient  shorthand,  if  any  option  settings  are
-      required  at  the  start  of a non-capturing subpattern, the
-      option letters may appear between the "?" and the ":".  Thus
-      the two patterns
-        (?i:saturday|sunday)
-        (?:(?i)saturday|sunday)
-      match exactly the same set of strings.  Because  alternative
-      branches  are  tried from left to right, and options are not
-      reset until the end of the subpattern is reached, an  option
-      setting  in  one  branch does affect subsequent branches, so
-      the above patterns match "SUNDAY" as well as "Saturday".
+        Subpatterns are delimited by parentheses (round brackets), which can be
+        nested.  Turning part of a pattern into a subpattern does two things:
+. It localizes a set of alternatives. For example, the pattern
+          cat(aract|erpillar|)
+        matches  one  of the words "cat", "cataract", or "caterpillar". Without
+        the parentheses, it would match "cataract",  "erpillar"  or  the  empty
+        string.
+.  It  sets  up  the  subpattern as a capturing subpattern. This means
+        that, when the whole pattern  matches,  that  portion  of  the  subject
+        string that matched the subpattern is passed back to the caller via the
+        ovector argument of pcre_exec(). Opening parentheses are  counted  from
+        left  to  right  (starting  from 1) to obtain numbers for the capturing
+        subpatterns.
+        For example, if the string "the red king" is matched against  the  pat-
+        tern
+          the ((red|white) (king|queen))
+        the captured substrings are "red king", "red", and "king", and are num-
+        bered 1, 2, and 3, respectively.
+        The fact that plain parentheses fulfil  two  functions  is  not  always
+        helpful.   There are often times when a grouping subpattern is required
+        without a capturing requirement. If an opening parenthesis is  followed
+        by  a question mark and a colon, the subpattern does not do any captur-
+        ing, and is not counted when computing the  number  of  any  subsequent
+        capturing  subpatterns. For example, if the string "the white queen" is
+        matched against the pattern
+          the ((?:red|white) (king|queen))
+        the captured substrings are "white queen" and "queen", and are numbered
+ and 2. The maximum number of capturing subpatterns is 65535, and the
+        maximum depth of nesting of all subpatterns, both  capturing  and  non-
+        capturing, is 200.
+        As  a  convenient shorthand, if any option settings are required at the
+        start of a non-capturing subpattern,  the  option  letters  may  appear
+        between the "?" and the ":". Thus the two patterns
+          (?i:saturday|sunday)
+          (?:(?i)saturday|sunday)
+        match exactly the same set of strings. Because alternative branches are
+        tried from left to right, and options are not reset until  the  end  of
+        the  subpattern is reached, an option setting in one branch does affect
+        subsequent branches, so the above patterns match "SUNDAY"  as  well  as
+        "Saturday".
+ NAMED SUBPATTERNS
+        Identifying  capturing  parentheses  by number is simple, but it can be
+        very hard to keep track of the numbers in complicated  regular  expres-
+        sions.  Furthermore,  if  an  expression  is  modified, the numbers may
+        change. To help with this difficulty, PCRE supports the naming of  sub-
+        patterns,  something  that  Perl  does  not  provide. The Python syntax
+        (?P<name>...) is used. Names consist  of  alphanumeric  characters  and
+        underscores, and must be unique within a pattern.
+        Named  capturing  parentheses  are  still  allocated numbers as well as
+        names. The PCRE API provides function calls for extracting the name-to-
+        number  translation table from a compiled pattern. There is also a con-
+        venience function for extracting a captured substring by name. For fur-
+        ther details see the pcreapi documentation.
  REPETITION
-      Repetition is specified by quantifiers, which can follow any
-      of the following items:
-        a single character, possibly escaped
+        Repetition  is  specified  by  quantifiers, which can follow any of the
-        the . metacharacter
+        following items:
-        a character class
-        a back reference (see next section)
+          a literal data character
-        a parenthesized subpattern (unless it is  an  assertion  -
+          the . metacharacter
-      see below)
+          the \C escape sequence
+          the \X escape sequence (in UTF-8 mode with Unicode properties)
-      The general repetition quantifier specifies  a  minimum  and
+          an escape such as \d that matches a single character
-      maximum  number  of  permitted  matches,  by  giving the two
+          a character class
-      numbers in curly brackets (braces), separated  by  a  comma.
+          a back reference (see next section)
-      The  numbers  must be less than 65536, and the first must be
+          a parenthesized subpattern (unless it is an assertion)
-      less than or equal to the second. For example:
+        The general repetition quantifier specifies a minimum and maximum  num-
-        z{2,4}
+        ber  of  permitted matches, by giving the two numbers in curly brackets
+        (braces), separated by a comma. The numbers must be  less  than  65536,
-      matches "zz", "zzz", or "zzzz". A closing brace on  its  own
+        and the first must be less than or equal to the second. For example:
-      is not a special character. If the second number is omitted,
-      but the comma is present, there is no upper  limit;  if  the
+          z{2,4}
-      second number and the comma are both omitted, the quantifier
-      specifies an exact number of required matches. Thus
+        matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a
+        special character. If the second number is omitted, but  the  comma  is
-        [aeiou]{3,}
+        present,  there  is  no upper limit; if the second number and the comma
+        are both omitted, the quantifier specifies an exact number of  required
-      matches at least 3 successive vowels,  but  may  match  many
+        matches. Thus
-      more, while
+          [aeiou]{3,}
-        \d{8}
+        matches at least 3 successive vowels, but may match many more, while
-      matches exactly 8 digits.  An  opening  curly  bracket  that
-      appears  in a position where a quantifier is not allowed, or
+          \d{8}
-      one that does not match the syntax of a quantifier, is taken
-      as  a literal character. For example, {,6} is not a quantif-
+        matches  exactly  8  digits. An opening curly bracket that appears in a
-      ier, but a literal string of four characters.
+        position where a quantifier is not allowed, or one that does not  match
+        the  syntax of a quantifier, is taken as a literal character. For exam-
-      The quantifier {0} is permitted, causing the  expression  to
+        ple, {,6} is not a quantifier, but a literal string of four characters.
-      behave  as  if the previous item and the quantifier were not
-      present.
+        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-
-      For convenience (and  historical  compatibility)  the  three
+        acters, each of which is represented by a two-byte sequence. Similarly,
-      most common quantifiers have single-character abbreviations:
+        when Unicode property support is available, \X{3} matches three Unicode
+        extended  sequences,  each of which may be several bytes long (and they
-        *    is equivalent to {0,}
+        may be of different lengths).
-        +    is equivalent to {1,}
-        ?    is equivalent to {0,1}
+        The quantifier {0} is permitted, causing the expression to behave as if
+        the previous item and the quantifier were not present.
-      It is possible to construct infinite loops  by  following  a
-      subpattern  that  can  match no characters with a quantifier
+        For  convenience  (and  historical compatibility) the three most common
-      that has no upper limit, for example:
+        quantifiers have single-character abbreviations:
-        (a?)*
+          *    is equivalent to {0,}
+          +    is equivalent to {1,}
-      Earlier versions of Perl and PCRE used to give an  error  at
+          ?    is equivalent to {0,1}
-      compile  time  for such patterns. However, because there are
-      cases where this  can  be  useful,  such  patterns  are  now
+        It is possible to construct infinite loops by  following  a  subpattern
-      accepted,  but  if  any repetition of the subpattern does in
+        that can match no characters with a quantifier that has no upper limit,
-      fact match no characters, the loop is forcibly broken.
+        for example:
-      By default, the quantifiers  are  "greedy",  that  is,  they
+          (a?)*
-      match  as much as possible (up to the maximum number of per-
-      mitted times), without causing the rest of  the  pattern  to
+        Earlier versions of Perl and PCRE used to give an error at compile time
-      fail. The classic example of where this gives problems is in
+        for  such  patterns. However, because there are cases where this can be
-      trying to match comments in C programs. These appear between
+        useful, such patterns are now accepted, but if any  repetition  of  the
-      the  sequences /* and */ and within the sequence, individual
+        subpattern  does in fact match no characters, the loop is forcibly bro-
-      * and / characters may appear. An attempt to  match  C  com-
+        ken.
-      ments by applying the pattern
+        By default, the quantifiers are "greedy", that is, they match  as  much
-        /\*.*\*/
+        as  possible  (up  to  the  maximum number of permitted times), without
+        causing the rest of the pattern to fail. The classic example  of  where
-      to the string
+        this gives problems is in trying to match comments in C programs. These
+        appear between /* and */ and within the comment,  individual  *  and  /
-        /* first command */  not comment  /* second comment */
+        characters  may  appear. An attempt to match C comments by applying the
+        pattern
-      fails, because it matches  the  entire  string  due  to  the
-      greediness of the .*  item.
+          /\*.*\*/
-      However, if a quantifier is followed by a question mark,  it
+        to the string
-      ceases  to be greedy, and instead matches the minimum number
-      of times possible, so the pattern
+          /* first comment */  not comment  /* second comment */
-        /\*.*?\*/
+        fails, because it matches the entire string owing to the greediness  of
+        the .*  item.
-      does the right thing with the C comments. The meaning of the
-      various  quantifiers is not otherwise changed, just the pre-
+        However,  if  a quantifier is followed by a question mark, it ceases to
-      ferred number of matches.  Do not confuse this use of  ques-
+        be greedy, and instead matches the minimum number of times possible, so
-      tion  mark  with  its  use as a quantifier in its own right.
+        the pattern
-      Because it has two uses, it can sometimes appear doubled, as
-      in
+          /\*.*?\*/
-        \d??\d
+        does  the  right  thing with the C comments. The meaning of the various
+        quantifiers is not otherwise changed,  just  the  preferred  number  of
-      which matches one digit by preference, but can match two  if
+        matches.   Do  not  confuse this use of question mark with its use as a
-      that is the only way the rest of the pattern matches.
+        quantifier in its own right. Because it has two uses, it can  sometimes
+        appear doubled, as in
-      If the PCRE_UNGREEDY option is set (an option which  is  not
-      available  in  Perl),  the  quantifiers  are  not  greedy by
+          \d??\d
-      default, but individual ones can be made greedy by following
-      them  with  a  question mark. In other words, it inverts the
+        which matches one digit by preference, but can match two if that is the
-      default behaviour.
+        only way the rest of the pattern matches.
-      When a parenthesized subpattern is quantified with a minimum
+        If the PCRE_UNGREEDY option is set (an option which is not available in
-      repeat  count  that is greater than 1 or with a limited max-
+        Perl),  the  quantifiers are not greedy by default, but individual ones
-      imum, more store is required for the  compiled  pattern,  in
+        can be made greedy by following them with a  question  mark.  In  other
-      proportion to the size of the minimum or maximum.
+        words, it inverts the default behaviour.
-      If a pattern starts with .* or  .{0,}  and  the  PCRE_DOTALL
+        When  a  parenthesized  subpattern  is quantified with a minimum repeat
-      option (equivalent to Perl's /s) is set, thus allowing the .
+        count that is greater than 1 or with a limited maximum, more memory  is
-      to match  newlines,  the  pattern  is  implicitly  anchored,
+        required  for  the  compiled  pattern, in proportion to the size of the
-      because whatever follows will be tried against every charac-
+        minimum or maximum.
-      ter position in the subject string, so there is no point  in
-      retrying  the overall match at any position after the first.
+        If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
-      PCRE treats such a pattern as though it were preceded by \A.
+        alent  to Perl's /s) is set, thus allowing the . to match newlines, the
-      In  cases where it is known that the subject string contains
+        pattern is implicitly anchored, because whatever follows will be  tried
-      no newlines, it is worth setting PCRE_DOTALL when  the  pat-
+        against  every character position in the subject string, so there is no
-      tern begins with .* in order to obtain this optimization, or
+        point in retrying the overall match at any position  after  the  first.
-      alternatively using ^ to indicate anchoring explicitly.
+        PCRE normally treats such a pattern as though it were preceded by \A.
-      When a capturing subpattern is repeated, the value  captured
+        In  cases  where  it  is known that the subject string contains no new-
-      is the substring that matched the final iteration. For exam-
+        lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-
-      ple, after
+        mization, or alternatively using ^ to indicate anchoring explicitly.
-        (tweedle[dume]{3}\s*)+
+        However,  there is one situation where the optimization cannot be used.
+        When .*  is inside capturing parentheses that  are  the  subject  of  a
-      has matched "tweedledum tweedledee" the value  of  the  cap-
+        backreference  elsewhere in the pattern, a match at the start may fail,
-      tured  substring  is  "tweedledee".  However,  if  there are
+        and a later one succeed. Consider, for example:
-      nested capturing  subpatterns,  the  corresponding  captured
-      values  may  have been set in previous iterations. For exam-
-      ple, after
-        /(a|(b))+/
+          (.*)abc\1
-      matches "aba" the value of the second captured substring  is
+        If the subject is "xyz123abc123" the match point is the fourth  charac-
-      "b".
+        ter. For this reason, such a pattern is not implicitly anchored.
+        When a capturing subpattern is repeated, the value captured is the sub-
+        string that matched the final iteration. For example, after
+          (tweedle[dume]{3}\s*)+
+        has matched "tweedledum tweedledee" the value of the captured substring
+        is  "tweedledee".  However,  if there are nested capturing subpatterns,
+        the corresponding captured values may have been set in previous  itera-
+        tions. For example, after
+          /(a|(b))+/