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

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-revision 488 by ph10,
Mon Jan 11 15:29:42 2010 UTC
+revision 507 by ph10,
Wed Mar 10 16:08:01 2010 UTC
 Line 29 
 INTRODUCTION
 .10, including support for UTF-8 encoded strings and  Unicode  general
         category  properties.  However,  UTF-8  and  Unicode  support has to be
         explicitly enabled; it is not the default. The  Unicode  tables  corre-
-        spond to Unicode release 5.1.
+        spond to Unicode release 5.2.0.
         In  addition to the Perl-compatible matching function, PCRE contains an
         alternative function that matches the same compiled patterns in a  dif-
 Line 263 
 AUTHOR
  REVISION
-        Last updated: 28 September 2009
+        Last updated: 01 March 2010
-        Copyright (c) 1997-2009 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------
 Line 3488 
 BACKSLASH
         Those that are not part of an identified script are lumped together  as
         "Common". The current list of scripts is:
-        Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
+        Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
-        Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
+        Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
-        Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
+        Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
-        Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
+        tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
-        gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
+        Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
-        Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
+        rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
-        Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
+        Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
-        Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
+        Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
-        Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
+        Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
+        Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
+        Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
+        Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
+        Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
+        Ugaritic, Vai, Yi.
-        Each  character has exactly one general category property, specified by
+        Each character has exactly one general category property, specified  by
         a two-letter abbreviation. For compatibility with Perl, negation can be
-        specified  by  including a circumflex between the opening brace and the
+        specified by including a circumflex between the opening brace  and  the
         property name. For example, \p{^Lu} is the same as \P{Lu}.
         If only one letter is specified with \p or \P, it includes all the gen-
-        eral  category properties that start with that letter. In this case, in
+        eral category properties that start with that letter. In this case,  in
-        the absence of negation, the curly brackets in the escape sequence  are
+        the  absence of negation, the curly brackets in the escape sequence are
         optional; these two examples have the same effect:
           \p{L}
-Line 3557 
 BACKSLASH
+Line 3562 
 BACKSLASH
           Zp    Paragraph separator
           Zs    Space separator
-        The  special property L& is also supported: it matches a character that
+        The special property L& is also supported: it matches a character  that
-        has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
+        has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
         classified as a modifier or "other".
-        The  Cs  (Surrogate)  property  applies only to characters in the range
+        The Cs (Surrogate) property applies only to  characters  in  the  range
-        U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
+        U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
-        ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
+        ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
         the pcreapi page). Perl does not support the Cs property.
-        The  long  synonyms  for  property  names  that  Perl supports (such as
+        The long synonyms for  property  names  that  Perl  supports  (such  as
-        \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
+        \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
         any of these properties with "Is".
         No character that is in the Unicode table has the Cn (unassigned) prop-
         erty.  Instead, this property is assumed for any code point that is not
         in the Unicode table.
-        Specifying  caseless  matching  does not affect these escape sequences.
+        Specifying caseless matching does not affect  these  escape  sequences.
         For example, \p{Lu} always matches only upper case letters.
-        The \X escape matches any number of Unicode  characters  that  form  an
+        The  \X  escape  matches  any number of Unicode characters that form an
         extended Unicode sequence. \X is equivalent to
           (?>\PM\pM*)
-        That  is,  it matches a character without the "mark" property, followed
+        That is, it matches a character without the "mark"  property,  followed
-        by zero or more characters with the "mark"  property,  and  treats  the
+        by  zero  or  more  characters with the "mark" property, and treats the
-        sequence  as  an  atomic group (see below).  Characters with the "mark"
+        sequence as an atomic group (see below).  Characters  with  the  "mark"
-        property are typically accents that  affect  the  preceding  character.
+        property  are  typically  accents  that affect the preceding character.
-        None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
+        None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
         matches any one character.
-        Matching characters by Unicode property is not fast, because  PCRE  has
+        Matching  characters  by Unicode property is not fast, because PCRE has
-        to  search  a  structure  that  contains data for over fifteen thousand
+        to search a structure that contains  data  for  over  fifteen  thousand
         characters. That is why the traditional escape sequences such as \d and
         \w do not use Unicode properties in PCRE.
     Resetting the match start
         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
-        ously matched characters not  to  be  included  in  the  final  matched
+        ously  matched  characters  not  to  be  included  in the final matched
         sequence. For example, the pattern:
           foo\Kbar
-        matches  "foobar",  but reports that it has matched "bar". This feature
+        matches "foobar", but reports that it has matched "bar".  This  feature
-        is similar to a lookbehind assertion (described  below).   However,  in
+        is  similar  to  a lookbehind assertion (described below).  However, in
-        this  case, the part of the subject before the real match does not have
+        this case, the part of the subject before the real match does not  have
-        to be of fixed length, as lookbehind assertions do. The use of \K  does
+        to  be of fixed length, as lookbehind assertions do. The use of \K does
-        not  interfere  with  the setting of captured substrings.  For example,
+        not interfere with the setting of captured  substrings.   For  example,
         when the pattern
           (foo)\Kbar
         matches "foobar", the first substring is still set to "foo".
+        Perl  documents  that  the  use  of  \K  within assertions is "not well
+        defined". In PCRE, \K is acted upon  when  it  occurs  inside  positive
+        assertions, but is ignored in negative assertions.
     Simple assertions
-        The final use of backslash is for certain simple assertions. An  asser-
+        The  final use of backslash is for certain simple assertions. An asser-
-        tion  specifies a condition that has to be met at a particular point in
+        tion specifies a condition that has to be met at a particular point  in
-        a match, without consuming any characters from the subject string.  The
+        a  match, without consuming any characters from the subject string. The
-        use  of subpatterns for more complicated assertions is described below.
+        use of subpatterns for more complicated assertions is described  below.
         The backslashed assertions are:
           \b     matches at a word boundary
-Line 3630 
 BACKSLASH
+Line 3639 
 BACKSLASH
           \z     matches only at the end of the subject
           \G     matches at the first matching position in the subject
-        These assertions may not appear in character classes (but note that  \b
+        These  assertions may not appear in character classes (but note that \b
         has a different meaning, namely the backspace character, inside a char-
         acter class).
-        A word boundary is a position in the subject string where  the  current
+        A  word  boundary is a position in the subject string where the current
-        character  and  the previous character do not both match \w or \W (i.e.
+        character and the previous character do not both match \w or  \W  (i.e.
-        one matches \w and the other matches \W), or the start or  end  of  the
+        one  matches  \w  and the other matches \W), or the start or end of the
         string if the first or last character matches \w, respectively. Neither
-        PCRE nor Perl has a separte "start of word" or "end  of  word"  metase-
+        PCRE  nor  Perl  has a separte "start of word" or "end of word" metase-
-        quence.  However,  whatever follows \b normally determines which it is.
+        quence. However, whatever follows \b normally determines which  it  is.
         For example, the fragment \ba matches "a" at the start of a word.
-        The \A, \Z, and \z assertions differ from  the  traditional  circumflex
+        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
+        at  the  very start and end of the subject string, whatever options are
-        set.  Thus,  they are independent of multiline mode. These three asser-
+        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.
+        affect only the behaviour of the circumflex and dollar  metacharacters.
-        However, if the startoffset argument of pcre_exec() is non-zero,  indi-
+        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
+        the  subject,  \A  can never match. The difference between \Z and \z is
         that \Z matches before a newline at the end of the string as well as at
         the very end, whereas \z matches only at the end.
-        The \G assertion is true only when the current matching position is  at
+        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
+        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
+        of  pcre_exec().  It  differs  from \A when the value of startoffset is
-        non-zero.  By calling pcre_exec() multiple times with appropriate argu-
+        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
+        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
+        end of the previous match. In Perl, these can  be  different  when  the
-        previously matched string was empty. Because PCRE does just  one  match
+        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
+        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.
-Line 3675 
 BACKSLASH
+Line 3684 
 BACKSLASH
  CIRCUMFLEX AND DOLLAR
         Outside a character class, in the default matching mode, the circumflex
-        character is an assertion that is true only  if  the  current  matching
+        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-
+        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
+        ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the
-        PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
+        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
+        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
+        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
+        alternative  in  which  it appears if the pattern is ever to match that
-        branch.  If all possible alternatives start with a circumflex, that is,
+        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-
+        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
+        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
+        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
+        matching point is at the end of  the  subject  string,  or  immediately
         before a newline at the end of the string (by default). Dollar need not
-        be  the  last  character of the pattern if a number of alternatives are
+        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
+        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
+        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
+        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,  a  circumflex
+        PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
-        matches  immediately after internal newlines as well as at the start of
+        matches immediately after internal newlines as well as at the start  of
-        the subject string. It does not match after a  newline  that  ends  the
+        the  subject  string.  It  does not match after a newline that ends the
-        string.  A dollar matches before any newlines in the string, as well as
+        string. A dollar matches before any newlines in the string, as well  as
-        at the very end, when PCRE_MULTILINE is set. When newline is  specified
+        at  the very end, when PCRE_MULTILINE is set. When newline is specified
-        as  the  two-character  sequence CRLF, isolated CR and LF characters do
+        as the two-character sequence CRLF, isolated CR and  LF  characters  do
         not indicate newlines.
-        For example, the pattern /^abc$/ matches the subject string  "def\nabc"
+        For  example, the pattern /^abc$/ matches the subject string "def\nabc"
-        (where  \n  represents a newline) in multiline mode, but not otherwise.
+        (where \n represents a newline) in multiline mode, but  not  otherwise.
-        Consequently, patterns that are anchored in single  line  mode  because
+        Consequently,  patterns  that  are anchored in single line mode because
-        all  branches  start  with  ^ are not anchored in multiline mode, and a
+        all branches start with ^ are not anchored in  multiline  mode,  and  a
-        match for circumflex is  possible  when  the  startoffset  argument  of
+        match  for  circumflex  is  possible  when  the startoffset argument of
-        pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if
+        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
+        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
+        and end of the subject in both modes, and if all branches of a  pattern
-        start with \A it is always anchored, whether or not  PCRE_MULTILINE  is
+        start  with  \A it is always anchored, whether or not PCRE_MULTILINE is
         set.
  FULL STOP (PERIOD, DOT)
         Outside a character class, a dot in the pattern matches any one charac-
-        ter in the subject string except (by default) a character  that  signi-
+        ter  in  the subject string except (by default) a character that signi-
-        fies  the  end  of  a line. In UTF-8 mode, the matched character may be
+        fies the end of a line. In UTF-8 mode, the  matched  character  may  be
         more than one byte long.
-        When a line ending is defined as a single character, dot never  matches
+        When  a line ending is defined as a single character, dot never matches
-        that  character; when the two-character sequence CRLF is used, dot does
+        that character; when the two-character sequence CRLF is used, dot  does
-        not match CR if it is immediately followed  by  LF,  but  otherwise  it
+        not  match  CR  if  it  is immediately followed by LF, but otherwise it
-        matches  all characters (including isolated CRs and LFs). When any Uni-
+        matches all characters (including isolated CRs and LFs). When any  Uni-
-        code line endings are being recognized, dot does not match CR or LF  or
+        code  line endings are being recognized, dot does not match CR or LF or
         any of the other line ending characters.
-        The  behaviour  of  dot  with regard to newlines can be changed. If the
+        The behaviour of dot with regard to newlines can  be  changed.  If  the
-        PCRE_DOTALL option is set, a dot matches  any  one  character,  without
+        PCRE_DOTALL  option  is  set,  a dot matches any one character, without
         exception. If the two-character sequence CRLF is present in the subject
         string, it takes two dots to match it.
-        The handling of dot is entirely independent of the handling of  circum-
+        The  handling of dot is entirely independent of the handling of circum-
-        flex  and  dollar,  the  only relationship being that they both involve
+        flex and dollar, the only relationship being  that  they  both  involve
         newlines. 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 always matches any
+        both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any
-        line-ending characters. The feature is provided in  Perl  in  order  to
+        line-ending  characters.  The  feature  is provided in Perl in order to
-        match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
+        match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-
-        acters into individual bytes, what remains in the string may be a  mal-
+        acters  into individual bytes, what remains in the string may be a mal-
-        formed  UTF-8  string.  For this reason, the \C escape sequence is best
+        formed UTF-8 string. For this reason, the \C escape  sequence  is  best
         avoided.
-        PCRE does not allow \C to appear in  lookbehind  assertions  (described
+        PCRE  does  not  allow \C to appear in lookbehind assertions (described
-        below),  because  in UTF-8 mode this would make it impossible to calcu-
+        below), because in UTF-8 mode this would make it impossible  to  calcu-
         late the length of the lookbehind.
-Line 3768 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3777 
 SQUARE BRACKETS AND CHARACTER CLASSES
         closing square bracket. A closing square bracket on its own is not spe-
         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
         a lone closing square bracket causes a compile-time error. If a closing
-        square bracket is required as a member of the class, it should  be  the
+        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
+        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
+        A  character  class matches a single character in the subject. In UTF-8
         mode, the character may be more than one byte long. A matched character
         must be in the set of characters defined by the class, unless the first
-        character  in  the  class definition is a circumflex, in which case the
+        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
+        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
+        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,
+        For  example, the character class [aeiou] matches any lower case vowel,
-        while  [^aeiou]  matches  any character that is not a 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
+        characters that are in the class by enumerating those that are  not.  A
-        class that starts with a circumflex is not an assertion; it still  con-
+        class  that starts with a circumflex is not an assertion; it still con-
-        sumes  a  character  from the subject string, and therefore it fails if
+        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  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
+        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
+        When  caseless  matching  is set, any letters in a class represent both
-        their  upper  case  and lower case versions, so for example, a caseless
+        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
+        [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not
-        match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always
+        match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always
-        understands the concept of case for characters whose  values  are  less
+        understands  the  concept  of case for characters whose values are less
-        than  128, so caseless matching is always possible. For characters with
+        than 128, so caseless matching is always possible. For characters  with
-        higher values, the concept of case is supported  if  PCRE  is  compiled
+        higher  values,  the  concept  of case is supported if PCRE is compiled
-        with  Unicode  property support, but not otherwise.  If you want to use
+        with Unicode property support, but not otherwise.  If you want  to  use
-        caseless matching in UTF8-mode for characters 128 and above,  you  must
+        caseless  matching  in UTF8-mode for characters 128 and above, you must
-        ensure  that  PCRE is compiled with Unicode property support as well as
+        ensure that PCRE is compiled with Unicode property support as  well  as
         with UTF-8 support.
-        Characters that might indicate line breaks are  never  treated  in  any
+        Characters  that  might  indicate  line breaks are never treated in any
-        special  way  when  matching  character  classes,  whatever line-ending
+        special way  when  matching  character  classes,  whatever  line-ending
-        sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
+        sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
         PCRE_MULTILINE options is used. A class such as [^a] always matches one
         of these characters.
-        The minus (hyphen) character can be used to specify a range of  charac-
+        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
+        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
+        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
+        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
+        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
+        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
+        two characters ("W" and "-") followed by a literal string "46]", so  it
-        would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a
+        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-
+        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.
+        preted  as a class containing a range followed by two other characters.
-        The  octal or hexadecimal representation of "]" can also be used to end
+        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
+        Ranges  operate in the collating sequence of character values. They can
-        also   be  used  for  characters  specified  numerically,  for  example
+        also  be  used  for  characters  specified  numerically,  for   example
-        [\000-\037]. In UTF-8 mode, ranges can include characters whose  values
+        [\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
+        to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
-        character tables for a French locale are in  use,  [\xc8-\xcb]  matches
+        character  tables  for  a French locale are in use, [\xc8-\xcb] matches
-        accented  E  characters in both cases. In UTF-8 mode, PCRE supports the
+        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
+        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
+        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
+        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
+        flex  can  conveniently  be used with the upper case character types to
-        specify  a  more  restricted  set of characters than the matching lower
+        specify a more restricted set of characters  than  the  matching  lower
-        case type. For example, the class [^\W_] matches any letter  or  digit,
+        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
+        The only metacharacters that are recognized in  character  classes  are
-        backslash, hyphen (only where it can be  interpreted  as  specifying  a
+        backslash,  hyphen  (only  where  it can be interpreted as specifying a
-        range),  circumflex  (only  at the start), opening square bracket (only
+        range), circumflex (only at the start), opening  square  bracket  (only
-        when it can be interpreted as introducing a POSIX class name - see  the
+        when  it can be interpreted as introducing a POSIX class name - see the
-        next  section),  and  the  terminating closing square bracket. However,
+        next section), and the terminating  closing  square  bracket.  However,
         escaping other non-alphanumeric characters does no harm.
  POSIX CHARACTER CLASSES
         Perl supports the POSIX notation for character classes. This uses names
-        enclosed  by  [: and :] within the enclosing square brackets. PCRE also
+        enclosed by [: and :] within the enclosing square brackets.  PCRE  also
         supports this notation. For example,
           [01[:alpha:]%]
-Line 3881 
 POSIX CHARACTER CLASSES
+Line 3890 
 POSIX CHARACTER CLASSES
           word     "word" characters (same as \w)
           xdigit   hexadecimal digits
-        The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
+        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
+        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
+        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
+        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
+        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.
-Line 3902 
 POSIX CHARACTER CLASSES
+Line 3911 
 POSIX CHARACTER CLASSES
  VERTICAL BAR
-        Vertical  bar characters are used to separate alternative patterns. For
+        Vertical bar characters are used to separate alternative patterns.  For
         example, the pattern
           gilbert|sullivan
-        matches either "gilbert" or "sullivan". Any number of alternatives  may
+        matches  either "gilbert" or "sullivan". Any number of alternatives may
-        appear,  and  an  empty  alternative  is  permitted (matching the empty
+        appear, and an empty  alternative  is  permitted  (matching  the  empty
         string). The matching process tries each alternative in turn, from left
-        to  right, and the first one that succeeds is used. If the alternatives
+        to right, and the first one that succeeds is used. If the  alternatives
-        are within a subpattern (defined below), "succeeds" means matching  the
+        are  within a subpattern (defined below), "succeeds" means matching the
         rest of the main pattern as well as the alternative in the subpattern.
  INTERNAL OPTION SETTING
-        The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
+        The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
-        PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from
+        PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
-        within  the  pattern  by  a  sequence  of  Perl option letters enclosed
+        within the pattern by  a  sequence  of  Perl  option  letters  enclosed
         between "(?" and ")".  The option letters are
           i  for PCRE_CASELESS
-Line 3929 
 INTERNAL OPTION SETTING
+Line 3938 
 INTERNAL OPTION SETTING
         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-
+        combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
-        LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,
+        LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
-        is also permitted. If a  letter  appears  both  before  and  after  the
+        is  also  permitted.  If  a  letter  appears  both before and after the
         hyphen, the option is unset.
-        The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
+        The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
-        can be changed in the same way as the Perl-compatible options by  using
+        can  be changed in the same way as the Perl-compatible options by using
         the characters J, U and X respectively.
-        When  one  of  these  option  changes occurs at top level (that is, not
+        When one of these option changes occurs at  top  level  (that  is,  not
-        inside subpattern parentheses), the change applies to the remainder  of
+        inside  subpattern 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 there-
         fore show up in data extracted by the pcre_fullinfo() function).
-        An  option  change  within a subpattern (see below for a description of
+        An option change within a subpattern (see below for  a  description  of
         subpatterns) affects only that part of the current 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
+        used).   By  this means, options can be made to have different settings
-        in  different parts of the pattern. Any changes made in one alternative
+        in different parts of the pattern. Any changes made in one  alternative
-        do carry on into subsequent branches within the  same  subpattern.  For
+        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
+        matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
-        first branch is abandoned before the option setting.  This  is  because
+        first  branch  is  abandoned before the option setting. This is because
-        the  effects  of option settings happen at compile time. There would be
+        the effects of option settings happen at compile time. There  would  be
         some very weird behaviour otherwise.
-        Note: There are other PCRE-specific options that  can  be  set  by  the
+        Note:  There  are  other  PCRE-specific  options that can be set by the
-        application  when  the  compile  or match functions are called. In some
+        application when the compile or match functions  are  called.  In  some
         cases the pattern can contain special leading sequences such as (*CRLF)
-        to  override  what  the application has set or what has been defaulted.
+        to override what the application has set or what  has  been  defaulted.
-        Details are given in the section entitled  "Newline  sequences"  above.
+        Details  are  given  in the section entitled "Newline sequences" above.
-        There  is  also  the  (*UTF8)  leading sequence that can be used to set
+        There is also the (*UTF8) leading sequence that  can  be  used  to  set
         UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
-Line 3981 
 SUBPATTERNS
+Line 3990 
 SUBPATTERNS
           cat(aract|erpillar|)
-        matches  one  of the words "cat", "cataract", or "caterpillar". Without
+        matches one of the words "cat", "cataract", or  "caterpillar".  Without
-        the parentheses, it would match  "cataract",  "erpillar"  or  an  empty
+        the  parentheses,  it  would  match  "cataract", "erpillar" or an empty
         string.
-.  It  sets  up  the  subpattern as a capturing subpattern. This means
+. It sets up the subpattern as  a  capturing  subpattern.  This  means
-        that, when the whole pattern  matches,  that  portion  of  the  subject
+        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
+        ovector  argument  of pcre_exec(). Opening parentheses are counted from
-        left  to  right  (starting  from 1) to obtain numbers for the capturing
+        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-
+        For  example,  if the string "the red king" is matched against the pat-
         tern
           the ((red|white) (king|queen))
-Line 4000 
 SUBPATTERNS
+Line 4009 
 SUBPATTERNS
         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
+        The  fact  that  plain  parentheses  fulfil two functions is not always
-        helpful.   There are often times when a grouping subpattern is required
+        helpful.  There are often times when a grouping subpattern is  required
-        without a capturing requirement. If an opening parenthesis is  followed
+        without  a capturing requirement. If an opening parenthesis is followed
-        by  a question mark and a colon, the subpattern does not do any captur-
+        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
+        ing,  and  is  not  counted when computing the number of any subsequent
-        capturing  subpatterns. For example, if the string "the white queen" is
+        capturing subpatterns. For example, if the string "the white queen"  is
         matched against the pattern
           the ((?:red|white) (king|queen))
-Line 4013 
 SUBPATTERNS
+Line 4022 
 SUBPATTERNS
         the captured substrings are "white queen" and "queen", and are numbered
 and 2. The maximum number of capturing subpatterns is 65535.
-        As  a  convenient shorthand, if any option settings are required at the
+        As a convenient shorthand, if any option settings are required  at  the
-        start of a non-capturing subpattern,  the  option  letters  may  appear
+        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
+        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
+        the subpattern is reached, an option setting in one branch does  affect
-        subsequent branches, so the above patterns match "SUNDAY"  as  well  as
+        subsequent  branches,  so  the above patterns match "SUNDAY" as well as
         "Saturday".
  DUPLICATE SUBPATTERN NUMBERS
         Perl 5.10 introduced a feature whereby each alternative in a subpattern
-        uses the same numbers for its capturing parentheses. Such a  subpattern
+        uses  the same numbers for its capturing parentheses. Such a subpattern
-        starts  with (?| and is itself a non-capturing subpattern. For example,
+        starts with (?| and is itself a non-capturing subpattern. For  example,
         consider this pattern:
           (?|(Sat)ur|(Sun))day
-        Because the two alternatives are inside a (?| group, both sets of  cap-
+        Because  the two alternatives are inside a (?| group, both sets of cap-
-        turing  parentheses  are  numbered one. Thus, when the pattern matches,
+        turing parentheses are numbered one. Thus, when  the  pattern  matches,
-        you can look at captured substring number  one,  whichever  alternative
+        you  can  look  at captured substring number one, whichever alternative
-        matched.  This  construct  is useful when you want to capture part, but
+        matched. This construct is useful when you want to  capture  part,  but
         not all, of one of a number of alternatives. Inside a (?| group, paren-
-        theses  are  numbered as usual, but the number is reset at the start of
+        theses are numbered as usual, but the number is reset at the  start  of
-        each branch. The numbers of any capturing buffers that follow the  sub-
+        each  branch. The numbers of any capturing buffers that follow the sub-
-        pattern  start after the highest number used in any branch. The follow-
+        pattern start after the highest number used in any branch. The  follow-
-        ing example is taken from the Perl documentation.  The  numbers  under-
+        ing  example  is taken from the Perl documentation.  The numbers under-
         neath show in which buffer the captured content will be stored.
           # before  ---------------branch-reset----------- after
           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
           # 1            2         2  3        2     3     4
-        A  back  reference  to a numbered subpattern uses the most recent value
+        A back reference to a numbered subpattern uses the  most  recent  value
-        that is set for that number by any subpattern.  The  following  pattern
+        that  is  set  for that number by any subpattern. The following pattern
         matches "abcabc" or "defdef":
           /(?|(abc)|(def))\1/
-        In  contrast, a recursive or "subroutine" call to a numbered subpattern
+        In contrast, a recursive or "subroutine" call to a numbered  subpattern
-        always refers to the first one in the pattern with  the  given  number.
+        always  refers  to  the first one in the pattern with the given number.
         The following pattern matches "abcabc" or "defabc":
           /(?|(abc)|(def))(?1)/
-        If  a condition test for a subpattern's having matched refers to a non-
+        If a condition test for a subpattern's having matched refers to a  non-
-        unique number, the test is true if any of the subpatterns of that  num-
+        unique  number, the test is true if any of the subpatterns of that num-
         ber have matched.
-        An  alternative approach to using this "branch reset" feature is to use
+        An alternative approach to using this "branch reset" feature is to  use
         duplicate named subpatterns, as described in the next section.
  NAMED SUBPATTERNS
-        Identifying capturing parentheses by number is simple, but  it  can  be
+        Identifying  capturing  parentheses  by number is simple, but it can be
-        very  hard  to keep track of the numbers in complicated regular expres-
+        very hard to keep track of the numbers in complicated  regular  expres-
-        sions. Furthermore, if an  expression  is  modified,  the  numbers  may
+        sions.  Furthermore,  if  an  expression  is  modified, the numbers may
-        change.  To help with this difficulty, PCRE supports the naming of sub-
+        change. To help with this difficulty, PCRE supports the naming of  sub-
         patterns. This feature was not added to Perl until release 5.10. Python
-        had  the  feature earlier, and PCRE introduced it at release 4.0, using
+        had the feature earlier, and PCRE introduced it at release  4.0,  using
-        the Python syntax. PCRE now supports both the Perl and the Python  syn-
+        the  Python syntax. PCRE now supports both the Perl and the Python syn-
-        tax.  Perl  allows  identically  numbered subpatterns to have different
+        tax. Perl allows identically numbered  subpatterns  to  have  different
         names, but PCRE does not.
-        In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)
+        In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
-        or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References
+        or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
-        to capturing parentheses from other parts of the pattern, such as  back
+        to  capturing parentheses from other parts of the pattern, such as back
-        references,  recursion,  and conditions, can be made by name as well as
+        references, recursion, and conditions, can be made by name as  well  as
         by number.
-        Names consist of up to  32  alphanumeric  characters  and  underscores.
+        Names  consist  of  up  to  32 alphanumeric characters and underscores.
-        Named  capturing  parentheses  are  still  allocated numbers as well as
+        Named capturing parentheses are still  allocated  numbers  as  well  as
-        names, exactly as if the names were not present. The PCRE API  provides
+        names,  exactly as if the names were not present. The PCRE API provides
         function calls for extracting the name-to-number translation table from
         a compiled pattern. There is also a convenience function for extracting
         a captured substring by name.
-        By  default, a name must be unique within a pattern, but it is possible
+        By default, a name must be unique within a pattern, but it is  possible
         to relax this constraint by setting the PCRE_DUPNAMES option at compile
-        time.  (Duplicate  names are also always permitted for subpatterns with
+        time. (Duplicate names are also always permitted for  subpatterns  with
-        the same number, set up as described in the previous  section.)  Dupli-
+        the  same  number, set up as described in the previous section.) Dupli-
-        cate  names  can  be useful for patterns where only one instance of the
+        cate names can be useful for patterns where only one  instance  of  the
-        named parentheses can match. Suppose you want to match the  name  of  a
+        named  parentheses  can  match. Suppose you want to match the name of a
-        weekday,  either as a 3-letter abbreviation or as the full name, and in
+        weekday, either as a 3-letter abbreviation or as the full name, and  in
         both cases you want to extract the abbreviation. This pattern (ignoring
         the line breaks) does the job:
-Line 4112 
 NAMED SUBPATTERNS
+Line 4121 
 NAMED SUBPATTERNS
           (?<DN>Thu)(?:rsday)?|
           (?<DN>Sat)(?:urday)?
-        There  are  five capturing substrings, but only one is ever set after a
+        There are five capturing substrings, but only one is ever set  after  a
         match.  (An alternative way of solving this problem is to use a "branch
         reset" subpattern, as described in the previous section.)
-        The  convenience  function  for extracting the data by name returns the
+        The convenience function for extracting the data by  name  returns  the
-        substring for the first (and in this example, the only)  subpattern  of
+        substring  for  the first (and in this example, the only) subpattern of
-        that  name  that  matched.  This saves searching to find which numbered
+        that name that matched. This saves searching  to  find  which  numbered
         subpattern it was.
-        If you make a back reference to  a  non-unique  named  subpattern  from
+        If  you  make  a  back  reference to a non-unique named subpattern from
-        elsewhere  in the pattern, the one that corresponds to the first occur-
+        elsewhere in the pattern, the one that corresponds to the first  occur-
         rence of the name is used. In the absence of duplicate numbers (see the
-        previous  section) this is the one with the lowest number. If you use a
+        previous section) this is the one with the lowest number. If you use  a
-        named reference in a condition test (see the section  about  conditions
+        named  reference  in a condition test (see the section about conditions
-        below),  either  to check whether a subpattern has matched, or to check
+        below), either to check whether a subpattern has matched, or  to  check
-        for recursion, all subpatterns with the same name are  tested.  If  the
+        for  recursion,  all  subpatterns with the same name are tested. If the
-        condition  is  true for any one of them, the overall condition is true.
+        condition is true for any one of them, the overall condition  is  true.
         This is the same behaviour as testing by number. For further details of
         the interfaces for handling named subpatterns, see the pcreapi documen-
         tation.
         Warning: You cannot use different names to distinguish between two sub-
-        patterns  with  the same number because PCRE uses only the numbers when
+        patterns with the same number because PCRE uses only the  numbers  when
         matching. For this reason, an error is given at compile time if differ-
-        ent  names  are given to subpatterns with the same number. However, you
+        ent names are given to subpatterns with the same number.  However,  you
-        can give the same name to subpatterns with the same number,  even  when
+        can  give  the same name to subpatterns with the same number, even when
         PCRE_DUPNAMES is not set.
  REPETITION
-        Repetition  is  specified  by  quantifiers, which can follow any of the
+        Repetition is specified by quantifiers, which can  follow  any  of  the
         following items:
           a literal data character
-Line 4157 
 REPETITION
+Line 4166 
 REPETITION
           a parenthesized subpattern (unless it is an assertion)
           a recursive or "subroutine" call to a subpattern
-        The general repetition quantifier specifies a minimum and maximum  num-
+        The  general repetition quantifier specifies a minimum and maximum num-
-        ber  of  permitted matches, by giving the two numbers in curly brackets
+        ber of permitted matches, by giving the two numbers in  curly  brackets
-        (braces), separated by a comma. The numbers must be  less  than  65536,
+        (braces),  separated  by  a comma. The numbers must be less than 65536,
         and the first must be less than or equal to the second. For example:
           z{2,4}
-        matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a
+        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
+        special  character.  If  the second number is omitted, but the comma is
-        present,  there  is  no upper limit; if the second number and the comma
+        present, there is no upper limit; if the second number  and  the  comma
-        are both omitted, the quantifier specifies an exact number of  required
+        are  both omitted, the quantifier specifies an exact number of required
         matches. Thus
           [aeiou]{3,}
-Line 4176 
 REPETITION
+Line 4185 
 REPETITION
           \d{8}
-        matches  exactly  8  digits. An opening curly bracket that appears in a
+        matches exactly 8 digits. An opening curly bracket that  appears  in  a
-        position where a quantifier is not allowed, or one that does not  match
+        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 syntax of a quantifier, is taken as a literal character. For  exam-
         ple, {,6} is not a quantifier, but a literal string of four characters.
-        In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to
+        In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to
         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-
         acters, each of which is represented by a two-byte sequence. Similarly,
         when Unicode property support is available, \X{3} matches three Unicode
-        extended sequences, each of which may be several bytes long  (and  they
+        extended  sequences,  each of which may be several bytes long (and they
         may be of different lengths).
         The quantifier {0} is permitted, causing the expression to behave as if
         the previous item and the quantifier were not present. This may be use-
-        ful  for  subpatterns that are referenced as subroutines from elsewhere
+        ful for subpatterns that are referenced as subroutines  from  elsewhere
         in the pattern. Items other than subpatterns that have a {0} quantifier
         are omitted from the compiled pattern.
-        For  convenience, the three most common quantifiers have single-charac-
+        For convenience, the three most common quantifiers have  single-charac-
         ter abbreviations:
           *    is equivalent to {0,}
           +    is equivalent to {1,}
           ?    is equivalent to {0,1}
-        It is possible to construct infinite loops by  following  a  subpattern
+        It  is  possible  to construct infinite loops by following a subpattern
         that can match no characters with a quantifier that has no upper limit,
         for example:
           (a?)*
         Earlier versions of Perl and PCRE used to give an error at compile time
-        for  such  patterns. However, because there are cases where this can be
+        for such patterns. However, because there are cases where this  can  be
-        useful, such patterns are now accepted, but if any  repetition  of  the
+        useful,  such  patterns  are now accepted, but if any repetition of the
-        subpattern  does in fact match no characters, the loop is forcibly bro-
+        subpattern does in fact match no characters, the loop is forcibly  bro-
         ken.
-        By default, the quantifiers are "greedy", that is, they match  as  much
+        By  default,  the quantifiers are "greedy", that is, they match as much
-        as  possible  (up  to  the  maximum number of permitted times), without
+        as possible (up to the maximum  number  of  permitted  times),  without
-        causing the rest of the pattern to fail. The classic example  of  where
+        causing  the  rest of the pattern to fail. The classic example of where
         this gives problems is in trying to match comments in C programs. These
-        appear between /* and */ and within the comment,  individual  *  and  /
+        appear  between  /*  and  */ and within the comment, individual * and /
-        characters  may  appear. An attempt to match C comments by applying the
+        characters may appear. An attempt to match C comments by  applying  the
         pattern
           /\*.*\*/
-Line 4227 
 REPETITION
+Line 4236 
 REPETITION
           /* first comment */  not comment  /* second comment */
-        fails, because it matches the entire string owing to the greediness  of
+        fails,  because it matches the entire string owing to the greediness of
         the .*  item.
-        However,  if  a quantifier is followed by a question mark, it ceases to
+        However, if a quantifier is followed by a question mark, it  ceases  to
         be greedy, and instead matches the minimum number of times possible, so
         the pattern
           /\*.*?\*/
-        does  the  right  thing with the C comments. The meaning of the various
+        does the right thing with the C comments. The meaning  of  the  various
-        quantifiers is not otherwise changed,  just  the  preferred  number  of
+        quantifiers  is  not  otherwise  changed,  just the preferred number of
-        matches.   Do  not  confuse this use of question mark with its use as a
+        matches.  Do not confuse this use of question mark with its  use  as  a
-        quantifier in its own right. Because it has two uses, it can  sometimes
+        quantifier  in its own right. Because it has two uses, it can sometimes
         appear doubled, as in
           \d??\d
-Line 4247 
 REPETITION
+Line 4256 
 REPETITION
         which matches one digit by preference, but can match two if that is the
         only way the rest of the pattern matches.
-        If the PCRE_UNGREEDY option is set (an option that is not available  in
+        If  the PCRE_UNGREEDY option is set (an option that is not available in
-        Perl),  the  quantifiers are not greedy by default, but individual ones
+        Perl), the quantifiers are not greedy by default, but  individual  ones
-        can be made greedy by following them with a  question  mark.  In  other
+        can  be  made  greedy  by following them with a question mark. In other
         words, it inverts the default behaviour.
-        When  a  parenthesized  subpattern  is quantified with a minimum repeat
+        When a parenthesized subpattern is quantified  with  a  minimum  repeat
-        count that is greater than 1 or with a limited maximum, more memory  is
+        count  that is greater than 1 or with a limited maximum, more memory is
-        required  for  the  compiled  pattern, in proportion to the size of the
+        required for the compiled pattern, in proportion to  the  size  of  the
         minimum or maximum.
         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
-        alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,
+        alent to Perl's /s) is set, thus allowing the dot  to  match  newlines,
-        the pattern is implicitly anchored, because whatever  follows  will  be
+        the  pattern  is  implicitly anchored, because whatever follows will be
-        tried  against every character position in the subject string, so there
+        tried against every character position in the subject string, so  there
-        is no point in retrying the overall match at  any  position  after  the
+        is  no  point  in  retrying the overall match at any position after the
-        first.  PCRE  normally treats such a pattern as though it were preceded
+        first. PCRE normally treats such a pattern as though it  were  preceded
         by \A.
-        In cases where it is known that the subject  string  contains  no  new-
+        In  cases  where  it  is known that the subject string contains no new-
-        lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-
+        lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-
         mization, or alternatively using ^ to indicate anchoring explicitly.
-        However, there is one situation where the optimization cannot be  used.
+        However,  there is one situation where the optimization cannot be used.
         When .*  is inside capturing parentheses that are the subject of a back
         reference elsewhere in the pattern, a match at the start may fail where
         a later one succeeds. Consider, for example:
           (.*)abc\1
-        If  the subject is "xyz123abc123" the match point is the fourth charac-
+        If the subject is "xyz123abc123" the match point is the fourth  charac-
         ter. For this reason, such a pattern is not implicitly anchored.
         When a capturing subpattern is repeated, the value captured is the sub-
-Line 4285 
 REPETITION
+Line 4294 
 REPETITION
           (tweedle[dume]{3}\s*)+
         has matched "tweedledum tweedledee" the value of the captured substring
-        is "tweedledee". However, if there are  nested  capturing  subpatterns,
+        is  "tweedledee".  However,  if there are nested capturing subpatterns,
-        the  corresponding captured values may have been set in previous itera-
+        the corresponding captured values may have been set in previous  itera-
         tions. For example, after
           /(a|(b))+/
-Line 4296 
 REPETITION
+Line 4305 
 REPETITION
  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
-        With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")
+        With  both  maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
-        repetition,  failure  of what follows normally causes the repeated item
+        repetition, failure of what follows normally causes the  repeated  item
-        to be re-evaluated to see if a different number of repeats  allows  the
+        to  be  re-evaluated to see if a different number of repeats allows the
-        rest  of  the pattern to match. Sometimes it is useful to prevent this,
+        rest of the pattern to match. Sometimes it is useful to  prevent  this,
-        either to change the nature of the match, or to cause it  fail  earlier
+        either  to  change the nature of the match, or to cause it fail earlier
-        than  it otherwise might, when the author of the pattern knows there is
+        than it otherwise might, when the author of the pattern knows there  is
         no point in carrying on.
-        Consider, for example, the pattern \d+foo when applied to  the  subject
+        Consider,  for  example, the pattern \d+foo when applied to the subject
         line
 bar
         After matching all 6 digits and then failing to match "foo", the normal
-        action of the matcher is to try again with only 5 digits  matching  the
+        action  of  the matcher is to try again with only 5 digits matching the
-        \d+  item,  and  then  with  4,  and  so on, before ultimately failing.
+        \d+ item, and then with  4,  and  so  on,  before  ultimately  failing.
-        "Atomic grouping" (a term taken from Jeffrey  Friedl's  book)  provides
+        "Atomic  grouping"  (a  term taken from Jeffrey Friedl's book) provides
-        the  means for specifying that once a subpattern has matched, it is not
+        the means for specifying that once a subpattern has matched, it is  not
         to be re-evaluated in this way.
-        If we use atomic grouping for the previous example, the  matcher  gives
+        If  we  use atomic grouping for the previous example, the matcher gives
-        up  immediately  on failing to match "foo" the first time. The notation
+        up immediately on failing to match "foo" the first time.  The  notation
         is a kind of special parenthesis, starting with (?> as in this example:
           (?>\d+)foo
-        This kind of parenthesis "locks up" the  part of the  pattern  it  con-
+        This  kind  of  parenthesis "locks up" the  part of the pattern it con-
-        tains  once  it  has matched, and a failure further into the pattern is
+        tains once it has matched, and a failure further into  the  pattern  is
-        prevented from backtracking into it. Backtracking past it  to  previous
+        prevented  from  backtracking into it. Backtracking past it to previous
         items, however, works as normal.
-        An  alternative  description  is that a subpattern of this type matches
+        An alternative description is that a subpattern of  this  type  matches
-        the string of characters that an  identical  standalone  pattern  would
+        the  string  of  characters  that an identical standalone pattern would
         match, if anchored at the current point in the subject string.
         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
         such as the above example can be thought of as a maximizing repeat that
-        must  swallow  everything  it can. So, while both \d+ and \d+? are pre-
+        must swallow everything it can. So, while both \d+ and  \d+?  are  pre-
-        pared to adjust the number of digits they match in order  to  make  the
+        pared  to  adjust  the number of digits they match in order to make the
         rest of the pattern match, (?>\d+) can only match an entire sequence of
         digits.
-        Atomic groups in general can of course contain arbitrarily  complicated
+        Atomic  groups in general can of course contain arbitrarily complicated
-        subpatterns,  and  can  be  nested. However, when the subpattern for an
+        subpatterns, and can be nested. However, when  the  subpattern  for  an
         atomic group is just a single repeated item, as in the example above, a
-        simpler  notation,  called  a "possessive quantifier" can be used. This
+        simpler notation, called a "possessive quantifier" can  be  used.  This
-        consists of an additional + character  following  a  quantifier.  Using
+        consists  of  an  additional  + character following a quantifier. Using
         this notation, the previous example can be rewritten as
           \d++foo
-Line 4352 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 4361 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
           (abc|xyz){2,3}+
-        Possessive  quantifiers  are  always  greedy;  the   setting   of   the
+        Possessive   quantifiers   are   always  greedy;  the  setting  of  the
         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
-        simpler forms of atomic group. However, there is no difference  in  the
+        simpler  forms  of atomic group. However, there is no difference in the
-        meaning  of  a  possessive  quantifier and the equivalent atomic group,
+        meaning of a possessive quantifier and  the  equivalent  atomic  group,
-        though there may be a performance  difference;  possessive  quantifiers
+        though  there  may  be a performance difference; possessive quantifiers
         should be slightly faster.
-        The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-
+        The possessive quantifier syntax is an extension to the Perl  5.8  syn-
-        tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first
+        tax.   Jeffrey  Friedl  originated the idea (and the name) in the first
         edition of his book. Mike McCloskey liked it, so implemented it when he
-        built Sun's Java package, and PCRE copied it from there. It  ultimately
+        built  Sun's Java package, and PCRE copied it from there. It ultimately
         found its way into Perl at release 5.10.
         PCRE has an optimization that automatically "possessifies" certain sim-
-        ple pattern constructs. For example, the sequence  A+B  is  treated  as
+        ple  pattern  constructs.  For  example, the sequence A+B is treated as
-        A++B  because  there is no point in backtracking into a sequence of A's
+        A++B because there is no point in backtracking into a sequence  of  A's
         when B must follow.
-        When a pattern contains an unlimited repeat inside  a  subpattern  that
+        When  a  pattern  contains an unlimited repeat inside a subpattern that
-        can  itself  be  repeated  an  unlimited number of times, the use of an
+        can itself be repeated an unlimited number of  times,  the  use  of  an
-        atomic group is the only way to avoid some  failing  matches  taking  a
+        atomic  group  is  the  only way to avoid some failing matches taking a
         very long time indeed. The pattern
           (\D+|<\d+>)*[!?]
-        matches  an  unlimited number of substrings that either consist of non-
+        matches an unlimited number of substrings that either consist  of  non-
-        digits, or digits enclosed in <>, followed by either ! or  ?.  When  it
+        digits,  or  digits  enclosed in <>, followed by either ! or ?. When it
         matches, it runs quickly. However, if it is applied to
           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-        it  takes  a  long  time  before reporting failure. This is because the
+        it takes a long time before reporting  failure.  This  is  because  the
-        string can be divided between the internal \D+ repeat and the  external
+        string  can be divided between the internal \D+ repeat and the external
-        *  repeat  in  a  large  number of ways, and all have to be tried. (The
+        * repeat in a large number of ways, and all  have  to  be  tried.  (The
-        example uses [!?] rather than a single character at  the  end,  because
+        example  uses  [!?]  rather than a single character at the end, because
-        both  PCRE  and  Perl have an optimization that allows for fast failure
+        both PCRE and Perl have an optimization that allows  for  fast  failure
-        when a single character is used. They remember the last single  charac-
+        when  a single character is used. They remember the last single charac-
-        ter  that  is required for a match, and fail early if it is not present
+        ter that is required for a match, and fail early if it is  not  present
-        in the string.) If the pattern is changed so that  it  uses  an  atomic
+        in  the  string.)  If  the pattern is changed so that it uses an atomic
         group, like this:
           ((?>\D+)|<\d+>)*[!?]
-Line 4402 
 BACK REFERENCES
+Line 4411 
 BACK REFERENCES
         Outside a character class, a backslash followed by a digit greater than
 (and possibly further digits) is a back reference to a capturing sub-
-        pattern  earlier  (that is, to its left) in the pattern, provided there
+        pattern earlier (that is, to its left) in the pattern,  provided  there
         have been that many previous capturing left parentheses.
         However, if the decimal number following the backslash is less than 10,
-        it  is  always  taken  as a back reference, and causes an error only if
+        it is always taken as a back reference, and causes  an  error  only  if
-        there are not that many capturing left parentheses in the  entire  pat-
+        there  are  not that many capturing left parentheses in the entire pat-
-        tern.  In  other words, the parentheses that are referenced need not be
+        tern. In other words, the parentheses that are referenced need  not  be
-        to the left of the reference for numbers less than 10. A "forward  back
+        to  the left of the reference for numbers less than 10. A "forward back
-        reference"  of  this  type can make sense when a repetition is involved
+        reference" of this type can make sense when a  repetition  is  involved
-        and the subpattern to the right has participated in an  earlier  itera-
+        and  the  subpattern to the right has participated in an earlier itera-
         tion.
-        It  is  not  possible to have a numerical "forward back reference" to a
+        It is not possible to have a numerical "forward back  reference"  to  a
-        subpattern whose number is 10 or  more  using  this  syntax  because  a
+        subpattern  whose  number  is  10  or  more using this syntax because a
-        sequence  such  as  \50 is interpreted as a character defined in octal.
+        sequence such as \50 is interpreted as a character  defined  in  octal.
         See the subsection entitled "Non-printing characters" above for further
-        details  of  the  handling of digits following a backslash. There is no
+        details of the handling of digits following a backslash.  There  is  no
-        such problem when named parentheses are used. A back reference  to  any
+        such  problem  when named parentheses are used. A back reference to any
         subpattern is possible using named parentheses (see below).
-        Another  way  of  avoiding  the ambiguity inherent in the use of digits
+        Another way of avoiding the ambiguity inherent in  the  use  of  digits
         following a backslash is to use the \g escape sequence, which is a fea-
-        ture  introduced  in  Perl  5.10.  This  escape  must be followed by an
+        ture introduced in Perl 5.10.  This  escape  must  be  followed  by  an
-        unsigned number or a negative number, optionally  enclosed  in  braces.
+        unsigned  number  or  a negative number, optionally enclosed in braces.
         These examples are all identical:
           (ring), \1
           (ring), \g1
           (ring), \g{1}
-        An  unsigned number specifies an absolute reference without the ambigu-
+        An unsigned number specifies an absolute reference without the  ambigu-
         ity that is present in the older syntax. It is also useful when literal
         digits follow the reference. A negative number is a relative reference.
         Consider this example:
-Line 4440 
 BACK REFERENCES
+Line 4449 
 BACK REFERENCES
           (abc(def)ghi)\g{-1}
         The sequence \g{-1} is a reference to the most recently started captur-
-        ing  subpattern  before \g, that is, is it equivalent to \2. Similarly,
+        ing subpattern before \g, that is, is it equivalent to  \2.  Similarly,
         \g{-2} would be equivalent to \1. The use of relative references can be
-        helpful  in  long  patterns,  and  also in patterns that are created by
+        helpful in long patterns, and also in  patterns  that  are  created  by
         joining together fragments that contain references within themselves.
-        A back reference matches whatever actually matched the  capturing  sub-
+        A  back  reference matches whatever actually matched the capturing sub-
-        pattern  in  the  current subject string, rather than anything matching
+        pattern in the current subject string, rather  than  anything  matching
         the subpattern itself (see "Subpatterns as subroutines" below for a way
         of doing that). So the pattern
           (sens|respons)e and \1ibility
-        matches  "sense and sensibility" and "response and responsibility", but
+        matches "sense and sensibility" and "response and responsibility",  but
-        not "sense and responsibility". If caseful matching is in force at  the
+        not  "sense and responsibility". If caseful matching is in force at the
-        time  of the back reference, the case of letters is relevant. For exam-
+        time of the back reference, the case of letters is relevant. For  exam-
         ple,
           ((?i)rah)\s+\1
-        matches "rah rah" and "RAH RAH", but not "RAH  rah",  even  though  the
+        matches  "rah  rah"  and  "RAH RAH", but not "RAH rah", even though the
         original capturing subpattern is matched caselessly.
-        There  are  several  different ways of writing back references to named
+        There are several different ways of writing back  references  to  named
-        subpatterns. The .NET syntax \k{name} and the Perl syntax  \k<name>  or
+        subpatterns.  The  .NET syntax \k{name} and the Perl syntax \k<name> or
-        \k'name'  are supported, as is the Python syntax (?P=name). Perl 5.10's
+        \k'name' are supported, as is the Python syntax (?P=name). Perl  5.10's
         unified back reference syntax, in which \g can be used for both numeric
-        and  named  references,  is  also supported. We could rewrite the above
+        and named references, is also supported. We  could  rewrite  the  above
         example in any of the following ways:
           (?<p1>(?i)rah)\s+\k<p1>
-Line 4474 
 BACK REFERENCES
+Line 4483 
 BACK REFERENCES
           (?P<p1>(?i)rah)\s+(?P=p1)
           (?<p1>(?i)rah)\s+\g{p1}
-        A subpattern that is referenced by  name  may  appear  in  the  pattern
+        A  subpattern  that  is  referenced  by  name may appear in the pattern
         before or after the reference.
-        There  may be more than one back reference to the same subpattern. If a
+        There may be more than one back reference to the same subpattern. If  a
-        subpattern has not actually been used in a particular match,  any  back
+        subpattern  has  not actually been used in a particular match, any back
         references to it always fail by default. For example, the pattern
           (a|(bc))\2
-        always  fails  if  it starts to match "a" rather than "bc". However, if
+        always fails if it starts to match "a" rather than  "bc".  However,  if
         the PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back refer-
         ence to an unset value matches an empty string.
-        Because  there may be many capturing parentheses in a pattern, all dig-
+        Because there may be many capturing parentheses in a pattern, all  dig-
-        its following a backslash are taken as part of a potential back  refer-
+        its  following a backslash are taken as part of a potential back refer-
-        ence  number.   If  the  pattern continues with a digit character, some
+        ence number.  If the pattern continues with  a  digit  character,  some
-        delimiter must  be  used  to  terminate  the  back  reference.  If  the
+        delimiter  must  be  used  to  terminate  the  back  reference.  If the
         PCRE_EXTENDED option is set, this can be whitespace. Otherwise, the \g{
         syntax or an empty comment (see "Comments" below) can be used.
     Recursive back references
-        A back reference that occurs inside the parentheses to which it  refers
+        A  back reference that occurs inside the parentheses to which it refers
-        fails  when  the subpattern is first used, so, for example, (a\1) never
+        fails when the subpattern is first used, so, for example,  (a\1)  never
-        matches.  However, such references can be useful inside  repeated  sub-
+        matches.   However,  such references can be useful inside repeated sub-
         patterns. For example, the pattern
           (a|b\1)+
         matches any number of "a"s and also "aba", "ababbaa" etc. At each iter-
-        ation of the subpattern,  the  back  reference  matches  the  character
+        ation  of  the  subpattern,  the  back  reference matches the character
-        string  corresponding  to  the previous iteration. In order for this to
+        string corresponding to the previous iteration. In order  for  this  to
-        work, the pattern must be such that the first iteration does  not  need
+        work,  the  pattern must be such that the first iteration does not need
-        to  match the back reference. This can be done using alternation, as in
+        to match the back reference. This can be done using alternation, as  in
         the example above, or by a quantifier with a minimum of zero.
-        Back references of this type cause the group that they reference to  be
+        Back  references of this type cause the group that they reference to be
-        treated  as  an atomic group.  Once the whole group has been matched, a
+        treated as an atomic group.  Once the whole group has been  matched,  a
-        subsequent matching failure cannot cause backtracking into  the  middle
+        subsequent  matching  failure cannot cause backtracking into the middle
         of the group.
  ASSERTIONS
-        An  assertion  is  a  test on the characters following or preceding the
+        An assertion is a test on the characters  following  or  preceding  the
-        current matching point that does not actually consume  any  characters.
+        current  matching  point that does not actually consume any characters.
-        The  simple  assertions  coded  as  \b, \B, \A, \G, \Z, \z, ^ and $ are
+        The simple assertions coded as \b, \B, \A, \G, \Z,  \z,  ^  and  $  are
         described above.
-        More complicated assertions are coded as  subpatterns.  There  are  two
+        More  complicated  assertions  are  coded as subpatterns. There are two
-        kinds:  those  that  look  ahead of the current position in the subject
+        kinds: those that look ahead of the current  position  in  the  subject
-        string, and those that look  behind  it.  An  assertion  subpattern  is
+        string,  and  those  that  look  behind  it. An assertion subpattern is
-        matched  in  the  normal way, except that it does not cause the current
+        matched in the normal way, except that it does not  cause  the  current
         matching position to be changed.
-        Assertion subpatterns are not capturing subpatterns,  and  may  not  be
+        Assertion  subpatterns  are  not  capturing subpatterns, and may not be
-        repeated,  because  it  makes no sense to assert the same thing several
+        repeated, because it makes no sense to assert the  same  thing  several
-        times. If any kind of assertion contains capturing  subpatterns  within
+        times.  If  any kind of assertion contains capturing subpatterns within
-        it,  these are counted for the purposes of numbering the capturing sub-
+        it, these are counted for the purposes of numbering the capturing  sub-
         patterns in the whole pattern.  However, substring capturing is carried
-        out  only  for  positive assertions, because it does not make sense for
+        out only for positive assertions, because it does not  make  sense  for
         negative assertions.
     Lookahead assertions
-Line 4544 
 ASSERTIONS
+Line 4553 
 ASSERTIONS
           \w+(?=;)
-        matches  a word followed by a semicolon, but does not include the semi-
+        matches a word followed by a semicolon, but does not include the  semi-
         colon in the match, and
           foo(?!bar)
-        matches any occurrence of "foo" that is not  followed  by  "bar".  Note
+        matches  any  occurrence  of  "foo" that is not followed by "bar". Note
         that the apparently similar pattern
           (?!foo)bar
-        does  not  find  an  occurrence  of "bar" that is preceded by something
+        does not find an occurrence of "bar"  that  is  preceded  by  something
-        other than "foo"; it finds any occurrence of "bar" whatsoever,  because
+        other  than "foo"; it finds any occurrence of "bar" whatsoever, because
         the assertion (?!foo) is always true when the next three characters are
         "bar". A lookbehind assertion is needed to achieve the other effect.
         If you want to force a matching failure at some point in a pattern, the
-        most  convenient  way  to  do  it  is with (?!) because an empty string
+        most convenient way to do it is  with  (?!)  because  an  empty  string
-        always matches, so an assertion that requires there not to be an  empty
+        always  matches, so an assertion that requires there not to be an empty
-        string  must  always  fail.   The  Perl  5.10 backtracking control verb
+        string must always fail.   The  Perl  5.10  backtracking  control  verb
         (*FAIL) or (*F) is essentially a synonym for (?!).
     Lookbehind assertions
-        Lookbehind assertions start with (?<= for positive assertions and  (?<!
+        Lookbehind  assertions start with (?<= for positive assertions and (?<!
         for negative assertions. For example,
           (?<!foo)bar
-        does  find  an  occurrence  of "bar" that is not preceded by "foo". The
+        does find an occurrence of "bar" that is not  preceded  by  "foo".  The
-        contents of a lookbehind assertion are restricted  such  that  all  the
+        contents  of  a  lookbehind  assertion are restricted such that all the
         strings it matches must have a fixed length. However, if there are sev-
-        eral top-level alternatives, they do not all  have  to  have  the  same
+        eral  top-level  alternatives,  they  do  not all have to have the same
         fixed length. Thus
           (?<=bullock|donkey)
-Line 4584 
 ASSERTIONS
+Line 4593 
 ASSERTIONS
           (?<!dogs?|cats?)
-        causes  an  error at compile time. Branches that match different length
+        causes an error at compile time. Branches that match  different  length
-        strings are permitted only at the top level of a lookbehind  assertion.
+        strings  are permitted only at the top level of a lookbehind assertion.
-        This  is an extension compared with Perl (5.8 and 5.10), which requires
+        This is an extension compared with Perl (5.8 and 5.10), which  requires
         all branches to match the same length of string. An assertion such as
           (?<=ab(c|de))
-        is not permitted, because its single top-level  branch  can  match  two
+        is  not  permitted,  because  its single top-level branch can match two
         different lengths, but it is acceptable to PCRE if rewritten to use two
         top-level branches:
           (?<=abc|abde)
         In some cases, the Perl 5.10 escape sequence \K (see above) can be used
-        instead  of  a  lookbehind  assertion  to  get  round  the fixed-length
+        instead of  a  lookbehind  assertion  to  get  round  the  fixed-length
         restriction.
-        The implementation of lookbehind assertions is, for  each  alternative,
+        The  implementation  of lookbehind assertions is, for each alternative,
-        to  temporarily  move the current position back by the fixed length and
+        to temporarily move the current position back by the fixed  length  and
         then try to match. If there are insufficient characters before the cur-
         rent position, the assertion fails.
         PCRE does not allow the \C escape (which matches a single byte in UTF-8
-        mode) to appear in lookbehind assertions, because it makes it  impossi-
+        mode)  to appear in lookbehind assertions, because it makes it impossi-
-        ble  to  calculate the length of the lookbehind. The \X and \R escapes,
+        ble to calculate the length of the lookbehind. The \X and  \R  escapes,
         which can match different numbers of bytes, are also not permitted.
-        "Subroutine" calls (see below) such as (?2) or (?&X) are  permitted  in
+        "Subroutine"  calls  (see below) such as (?2) or (?&X) are permitted in
-        lookbehinds,  as  long as the subpattern matches a fixed-length string.
+        lookbehinds, as long as the subpattern matches a  fixed-length  string.
         Recursion, however, is not supported.
-        Possessive quantifiers can  be  used  in  conjunction  with  lookbehind
+        Possessive  quantifiers  can  be  used  in  conjunction with lookbehind
         assertions to specify efficient matching of fixed-length strings at the
         end of subject strings. Consider a simple pattern such as
           abcd$
-        when applied to a long string that does  not  match.  Because  matching
+        when  applied  to  a  long string that does not match. Because matching
         proceeds from left to right, PCRE will look for each "a" in the subject
-        and then see if what follows matches the rest of the  pattern.  If  the
+        and  then  see  if what follows matches the rest of the pattern. If the
         pattern is specified as
           ^.*abcd$
-        the  initial .* matches the entire string at first, but when this fails
+        the initial .* matches the entire string at first, but when this  fails
         (because there is no following "a"), it backtracks to match all but the
-        last  character,  then all but the last two characters, and so on. Once
+        last character, then all but the last two characters, and so  on.  Once
-        again the search for "a" covers the entire string, from right to  left,
+        again  the search for "a" covers the entire string, from right to left,
         so we are no better off. However, if the pattern is written as
           ^.*+(?<=abcd)
-        there  can  be  no backtracking for the .*+ item; it can match only the
+        there can be no backtracking for the .*+ item; it can  match  only  the
-        entire string. The subsequent lookbehind assertion does a  single  test
+        entire  string.  The subsequent lookbehind assertion does a single test
-        on  the last four characters. If it fails, the match fails immediately.
+        on the last four characters. If it fails, the match fails  immediately.
-        For long strings, this approach makes a significant difference  to  the
+        For  long  strings, this approach makes a significant difference to the
         processing time.
     Using multiple assertions
-Line 4648 
 ASSERTIONS
+Line 4657 
 ASSERTIONS
           (?<=\d{3})(?<!999)foo
-        matches  "foo" preceded by three digits that are not "999". Notice that
+        matches "foo" preceded by three digits that are not "999". Notice  that
-        each of the assertions is applied independently at the  same  point  in
+        each  of  the  assertions is applied independently at the same point in
-        the  subject  string.  First  there  is a check that the previous three
+        the subject string. First there is a  check  that  the  previous  three
-        characters are all digits, and then there is  a  check  that  the  same
+        characters  are  all  digits,  and  then there is a check that the same
         three characters are not "999".  This pattern does not match "foo" pre-
-        ceded by six characters, the first of which are  digits  and  the  last
+        ceded  by  six  characters,  the first of which are digits and the last
-        three  of  which  are not "999". For example, it doesn't match "123abc-
+        three of which are not "999". For example, it  doesn't  match  "123abc-
         foo". A pattern to do that is
           (?<=\d{3}...)(?<!999)foo
-        This time the first assertion looks at the  preceding  six  characters,
+        This  time  the  first assertion looks at the preceding six characters,
         checking that the first three are digits, and then the second assertion
         checks that the preceding three characters are not "999".
-Line 4667 
 ASSERTIONS
+Line 4676 
 ASSERTIONS
           (?<=(?<!foo)bar)baz
-        matches an occurrence of "baz" that is preceded by "bar" which in  turn
+        matches  an occurrence of "baz" that is preceded by "bar" which in turn
         is not preceded by "foo", while
           (?<=\d{3}(?!999)...)foo
-        is  another pattern that matches "foo" preceded by three digits and any
+        is another pattern that matches "foo" preceded by three digits and  any
         three characters that are not "999".
  CONDITIONAL SUBPATTERNS
-        It is possible to cause the matching process to obey a subpattern  con-
+        It  is possible to cause the matching process to obey a subpattern con-
-        ditionally  or to choose between two alternative subpatterns, depending
+        ditionally or to choose between two alternative subpatterns,  depending
-        on the result of an assertion, or whether a specific capturing  subpat-
+        on  the result of an assertion, or whether a specific capturing subpat-
-        tern  has  already  been matched. The two possible forms of conditional
+        tern has already been matched. The two possible  forms  of  conditional
         subpattern are:
           (?(condition)yes-pattern)
           (?(condition)yes-pattern|no-pattern)
-        If the condition is satisfied, the yes-pattern is used;  otherwise  the
+        If  the  condition is satisfied, the yes-pattern is used; otherwise the
-        no-pattern  (if  present)  is used. If there are more than two alterna-
+        no-pattern (if present) is used. If there are more  than  two  alterna-
         tives in the subpattern, a compile-time error occurs.
-        There are four kinds of condition: references  to  subpatterns,  refer-
+        There  are  four  kinds of condition: references to subpatterns, refer-
         ences to recursion, a pseudo-condition called DEFINE, and assertions.
     Checking for a used subpattern by number
-        If  the  text between the parentheses consists of a sequence of digits,
+        If the text between the parentheses consists of a sequence  of  digits,
         the condition is true if a capturing subpattern of that number has pre-
-        viously  matched.  If  there is more than one capturing subpattern with
+        viously matched. If there is more than one  capturing  subpattern  with
-        the same number (see the earlier  section  about  duplicate  subpattern
+        the  same  number  (see  the earlier section about duplicate subpattern
         numbers), the condition is true if any of them have been set. An alter-
-        native notation is to precede the digits with a plus or minus sign.  In
+        native  notation is to precede the digits with a plus or minus sign. In
-        this  case, the subpattern number is relative rather than absolute. The
+        this case, the subpattern number is relative rather than absolute.  The
-        most recently opened parentheses can be referenced by (?(-1), the  next
+        most  recently opened parentheses can be referenced by (?(-1), the next
-        most  recent  by  (?(-2),  and so on. In looping constructs it can also
+        most recent by (?(-2), and so on. In looping  constructs  it  can  also
-        make sense to refer  to  subsequent  groups  with  constructs  such  as
+        make  sense  to  refer  to  subsequent  groups  with constructs such as
         (?(+2).
-        Consider  the  following  pattern, which contains non-significant white
+        Consider the following pattern, which  contains  non-significant  white
         space to make it more readable (assume the PCRE_EXTENDED option) and to
         divide it into three parts for ease of discussion:
           ( \( )?    [^()]+    (?(1) \) )
-        The  first  part  matches  an optional opening parenthesis, and if that
+        The first part matches an optional opening  parenthesis,  and  if  that
         character is present, sets it as the first captured substring. The sec-
-        ond  part  matches one or more characters that are not parentheses. The
+        ond part matches one or more characters that are not  parentheses.  The
         third part is a conditional subpattern that tests whether the first set
         of parentheses matched or not. If they did, that is, if subject started
         with an opening parenthesis, the condition is true, and so the yes-pat-
-        tern  is  executed  and  a  closing parenthesis is required. Otherwise,
+        tern is executed and a  closing  parenthesis  is  required.  Otherwise,
-        since no-pattern is not present, the  subpattern  matches  nothing.  In
+        since  no-pattern  is  not  present, the subpattern matches nothing. In
-        other  words,  this  pattern  matches  a  sequence  of non-parentheses,
+        other words,  this  pattern  matches  a  sequence  of  non-parentheses,
         optionally enclosed in parentheses.
-        If you were embedding this pattern in a larger one,  you  could  use  a
+        If  you  were  embedding  this pattern in a larger one, you could use a
         relative reference:
           ...other stuff... ( \( )?    [^()]+    (?(-1) \) ) ...
-        This  makes  the  fragment independent of the parentheses in the larger
+        This makes the fragment independent of the parentheses  in  the  larger
         pattern.
     Checking for a used subpattern by name
-        Perl uses the syntax (?(<name>)...) or (?('name')...)  to  test  for  a
+        Perl  uses  the  syntax  (?(<name>)...) or (?('name')...) to test for a
-        used  subpattern  by  name.  For compatibility with earlier versions of
+        used subpattern by name. For compatibility  with  earlier  versions  of
-        PCRE, which had this facility before Perl, the syntax  (?(name)...)  is
+        PCRE,  which  had this facility before Perl, the syntax (?(name)...) is
-        also  recognized. However, there is a possible ambiguity with this syn-
+        also recognized. However, there is a possible ambiguity with this  syn-
-        tax, because subpattern names may  consist  entirely  of  digits.  PCRE
+        tax,  because  subpattern  names  may  consist entirely of digits. PCRE
-        looks  first for a named subpattern; if it cannot find one and the name
+        looks first for a named subpattern; if it cannot find one and the  name
-        consists entirely of digits, PCRE looks for a subpattern of  that  num-
+        consists  entirely  of digits, PCRE looks for a subpattern of that num-
-        ber,  which must be greater than zero. Using subpattern names that con-
+        ber, which must be greater than zero. Using subpattern names that  con-
         sist entirely of digits is not recommended.
         Rewriting the above example to use a named subpattern gives this:
           (?<OPEN> \( )?    [^()]+    (?(<OPEN>) \) )
-        If the name used in a condition of this kind is a duplicate,  the  test
+        If  the  name used in a condition of this kind is a duplicate, the test
-        is  applied to all subpatterns of the same name, and is true if any one
+        is applied to all subpatterns of the same name, and is true if any  one
         of them has matched.
     Checking for pattern recursion
         If the condition is the string (R), and there is no subpattern with the
-        name  R, the condition is true if a recursive call to the whole pattern
+        name R, the condition is true if a recursive call to the whole  pattern
         or any subpattern has been made. If digits or a name preceded by amper-
         sand follow the letter R, for example:
-Line 4764 
 CONDITIONAL SUBPATTERNS
+Line 4773 
 CONDITIONAL SUBPATTERNS
         the condition is true if the most recent recursion is into a subpattern
         whose number or name is given. This condition does not check the entire
-        recursion  stack.  If  the  name  used in a condition of this kind is a
+        recursion stack. If the name used in a condition  of  this  kind  is  a
         duplicate, the test is applied to all subpatterns of the same name, and
         is true if any one of them is the most recent recursion.
-        At  "top  level",  all  these recursion test conditions are false.  The
+        At "top level", all these recursion test  conditions  are  false.   The
         syntax for recursive patterns is described below.
     Defining subpatterns for use by reference only
-        If the condition is the string (DEFINE), and  there  is  no  subpattern
+        If  the  condition  is  the string (DEFINE), and there is no subpattern
-        with  the  name  DEFINE,  the  condition is always false. In this case,
+        with the name DEFINE, the condition is  always  false.  In  this  case,
-        there may be only one alternative  in  the  subpattern.  It  is  always
+        there  may  be  only  one  alternative  in the subpattern. It is always
-        skipped  if  control  reaches  this  point  in the pattern; the idea of
+        skipped if control reaches this point  in  the  pattern;  the  idea  of
-        DEFINE is that it can be used to define "subroutines" that can be  ref-
+        DEFINE  is that it can be used to define "subroutines" that can be ref-
-        erenced  from elsewhere. (The use of "subroutines" is described below.)
+        erenced from elsewhere. (The use of "subroutines" is described  below.)
-        For example, a pattern to match an IPv4 address could be  written  like
+        For  example,  a pattern to match an IPv4 address could be written like
         this (ignore whitespace and line breaks):
           (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )
           \b (?&byte) (\.(?&byte)){3} \b
-        The  first part of the pattern is a DEFINE group inside which a another
+        The first part of the pattern is a DEFINE group inside which a  another
-        group named "byte" is defined. This matches an individual component  of
+        group  named "byte" is defined. This matches an individual component of
-        an  IPv4  address  (a number less than 256). When matching takes place,
+        an IPv4 address (a number less than 256). When  matching  takes  place,
-        this part of the pattern is skipped because DEFINE acts  like  a  false
+        this  part  of  the pattern is skipped because DEFINE acts like a false
-        condition.  The  rest of the pattern uses references to the named group
+        condition. The rest of the pattern uses references to the  named  group
-        to match the four dot-separated components of an IPv4 address,  insist-
+        to  match the four dot-separated components of an IPv4 address, insist-
         ing on a word boundary at each end.
     Assertion conditions
-        If  the  condition  is  not  in any of the above formats, it must be an
+        If the condition is not in any of the above  formats,  it  must  be  an
-        assertion.  This may be a positive or negative lookahead or  lookbehind
+        assertion.   This may be a positive or negative lookahead or lookbehind
-        assertion.  Consider  this  pattern,  again  containing non-significant
+        assertion. Consider  this  pattern,  again  containing  non-significant
         white space, and with the two alternatives on the second line:
           (?(?=[^a-z]*[a-z])
           \d{2}-[a-z]{3}-\d{2}  |  \d{2}-\d{2}-\d{2} )
-        The condition  is  a  positive  lookahead  assertion  that  matches  an
+        The  condition  is  a  positive  lookahead  assertion  that  matches an
-        optional  sequence of non-letters followed by a letter. In other words,
+        optional sequence of non-letters followed by a letter. In other  words,
-        it tests for the presence of at least one letter in the subject.  If  a
+        it  tests  for the presence of at least one letter in the subject. If a
-        letter  is found, the subject is matched against the first alternative;
+        letter is found, the subject is matched against the first  alternative;
-        otherwise it is  matched  against  the  second.  This  pattern  matches
+        otherwise  it  is  matched  against  the  second.  This pattern matches
-        strings  in  one  of the two forms dd-aaa-dd or dd-dd-dd, where aaa are
+        strings in one of the two forms dd-aaa-dd or dd-dd-dd,  where  aaa  are
         letters and dd are digits.
  COMMENTS
-        The sequence (?# marks the start of a comment that continues up to  the
+        The  sequence (?# marks the start of a comment that continues up to the
-        next  closing  parenthesis.  Nested  parentheses are not permitted. The
+        next closing parenthesis. Nested parentheses  are  not  permitted.  The
-        characters that make up a comment play no part in the pattern  matching
+        characters  that make up a comment play no part in the pattern matching
         at all.
-        If  the PCRE_EXTENDED option is set, an unescaped # character outside a
+        If the PCRE_EXTENDED option is set, an unescaped # character outside  a
-        character class introduces a  comment  that  continues  to  immediately
+        character  class  introduces  a  comment  that continues to immediately
         after the next newline in the pattern.
  RECURSIVE PATTERNS
-        Consider  the problem of matching a string in parentheses, allowing for
+        Consider the problem of matching a string in parentheses, allowing  for
-        unlimited nested parentheses. Without the use of  recursion,  the  best
+        unlimited  nested  parentheses.  Without the use of recursion, the best
-        that  can  be  done  is  to use a pattern that matches up to some fixed
+        that can be done is to use a pattern that  matches  up  to  some  fixed
-        depth of nesting. It is not possible to  handle  an  arbitrary  nesting
+        depth  of  nesting.  It  is not possible to handle an arbitrary nesting
         depth.
         For some time, Perl has provided a facility that allows regular expres-
-        sions to recurse (amongst other things). It does this by  interpolating
+        sions  to recurse (amongst other things). It does this by interpolating
-        Perl  code in the expression at run time, and the code can refer to the
+        Perl code in the expression at run time, and the code can refer to  the
         expression itself. A Perl pattern using code interpolation to solve the
         parentheses problem can be created like this:
-Line 4844 
 RECURSIVE PATTERNS
+Line 4853 
 RECURSIVE PATTERNS
         refers recursively to the pattern in which it appears.
         Obviously, PCRE cannot support the interpolation of Perl code. Instead,
-        it  supports  special  syntax  for recursion of the entire pattern, and
+        it supports special syntax for recursion of  the  entire  pattern,  and
-        also for individual subpattern recursion.  After  its  introduction  in
+        also  for  individual  subpattern  recursion. After its introduction in
-        PCRE  and  Python,  this  kind of recursion was subsequently introduced
+        PCRE and Python, this kind of  recursion  was  subsequently  introduced
         into Perl at release 5.10.
-        A special item that consists of (? followed by a  number  greater  than
+        A  special  item  that consists of (? followed by a number greater than
         zero and a closing parenthesis is a recursive call of the subpattern of
-        the given number, provided that it occurs inside that  subpattern.  (If
+        the  given  number, provided that it occurs inside that subpattern. (If
-        not,  it  is  a  "subroutine" call, which is described in the next sec-
+        not, it is a "subroutine" call, which is described  in  the  next  sec-
-        tion.) The special item (?R) or (?0) is a recursive call of the  entire
+        tion.)  The special item (?R) or (?0) is a recursive call of the entire
         regular expression.
-        This  PCRE  pattern  solves  the nested parentheses problem (assume the
+        This PCRE pattern solves the nested  parentheses  problem  (assume  the
         PCRE_EXTENDED option is set so that white space is ignored):
           \( ( [^()]++ | (?R) )* \)
-        First it matches an opening parenthesis. Then it matches any number  of
+        First  it matches an opening parenthesis. Then it matches any number of
-        substrings  which  can  either  be  a sequence of non-parentheses, or a
+        substrings which can either be a  sequence  of  non-parentheses,  or  a
-        recursive match of the pattern itself (that is, a  correctly  parenthe-
+        recursive  match  of the pattern itself (that is, a correctly parenthe-
         sized substring).  Finally there is a closing parenthesis. Note the use
         of a possessive quantifier to avoid backtracking into sequences of non-
         parentheses.
-        If  this  were  part of a larger pattern, you would not want to recurse
+        If this were part of a larger pattern, you would not  want  to  recurse
         the entire pattern, so instead you could use this:
           ( \( ( [^()]++ | (?1) )* \) )
-        We have put the pattern into parentheses, and caused the  recursion  to
+        We  have  put the pattern into parentheses, and caused the recursion to
         refer to them instead of the whole pattern.
-        In  a  larger  pattern,  keeping  track  of  parenthesis numbers can be
+        In a larger pattern,  keeping  track  of  parenthesis  numbers  can  be
-        tricky. This is made easier by the use of relative references  (a  Perl
+        tricky.  This  is made easier by the use of relative references (a Perl
-.10  feature).   Instead  of  (?1)  in the pattern above you can write
+.10 feature).  Instead of (?1) in the  pattern  above  you  can  write
         (?-2) to refer to the second most recently opened parentheses preceding
-        the  recursion.  In  other  words,  a  negative number counts capturing
+        the recursion. In other  words,  a  negative  number  counts  capturing
         parentheses leftwards from the point at which it is encountered.
-        It is also possible to refer to  subsequently  opened  parentheses,  by
+        It  is  also  possible  to refer to subsequently opened parentheses, by
-        writing  references  such  as (?+2). However, these cannot be recursive
+        writing references such as (?+2). However, these  cannot  be  recursive
-        because the reference is not inside the  parentheses  that  are  refer-
+        because  the  reference  is  not inside the parentheses that are refer-
-        enced.  They  are  always  "subroutine" calls, as described in the next
+        enced. They are always "subroutine" calls, as  described  in  the  next
         section.
-        An alternative approach is to use named parentheses instead.  The  Perl
+        An  alternative  approach is to use named parentheses instead. The Perl
-        syntax  for  this  is (?&name); PCRE's earlier syntax (?P>name) is also
+        syntax for this is (?&name); PCRE's earlier syntax  (?P>name)  is  also
         supported. We could rewrite the above example as follows:
           (?<pn> \( ( [^()]++ | (?&pn) )* \) )
-        If there is more than one subpattern with the same name,  the  earliest
+        If  there  is more than one subpattern with the same name, the earliest
         one is used.
-        This  particular  example pattern that we have been looking at contains
+        This particular example pattern that we have been looking  at  contains
         nested unlimited repeats, and so the use of a possessive quantifier for
         matching strings of non-parentheses is important when applying the pat-
-        tern to strings that do not match. For example, when  this  pattern  is
+        tern  to  strings  that do not match. For example, when this pattern is
         applied to
           (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa()
-        it  yields  "no  match" quickly. However, if a possessive quantifier is
+        it yields "no match" quickly. However, if a  possessive  quantifier  is
-        not used, the match runs for a very long time indeed because there  are
+        not  used, the match runs for a very long time indeed because there are
-        so  many  different  ways the + and * repeats can carve up the subject,
+        so many different ways the + and * repeats can carve  up  the  subject,
         and all have to be tested before failure can be reported.
-        At the end of a match, the values of capturing  parentheses  are  those
+        At  the  end  of a match, the values of capturing parentheses are those
-        from  the outermost level. If you want to obtain intermediate values, a
+        from the outermost level. If you want to obtain intermediate values,  a
-        callout function can be used (see below and the pcrecallout  documenta-
+        callout  function can be used (see below and the pcrecallout documenta-
         tion). If the pattern above is matched against
           (ab(cd)ef)
-        the  value  for  the  inner capturing parentheses (numbered 2) is "ef",
+        the value for the inner capturing parentheses  (numbered  2)  is  "ef",
-        which is the last value taken on at the top level. If a capturing  sub-
+        which  is the last value taken on at the top level. If a capturing sub-
         pattern is not matched at the top level, its final value is unset, even
         if it is (temporarily) set at a deeper level.
-        If there are more than 15 capturing parentheses in a pattern, PCRE  has
+        If  there are more than 15 capturing parentheses in a pattern, PCRE has
-        to  obtain extra memory to store data during a recursion, which it does
+        to obtain extra memory to store data during a recursion, which it  does
         by using pcre_malloc, freeing it via pcre_free afterwards. If no memory
         can be obtained, the match fails with the PCRE_ERROR_NOMEMORY error.
-        Do  not  confuse  the (?R) item with the condition (R), which tests for
+        Do not confuse the (?R) item with the condition (R),  which  tests  for
-        recursion.  Consider this pattern, which matches text in  angle  brack-
+        recursion.   Consider  this pattern, which matches text in angle brack-
-        ets,  allowing for arbitrary nesting. Only digits are allowed in nested
+        ets, allowing for arbitrary nesting. Only digits are allowed in  nested
-        brackets (that is, when recursing), whereas any characters are  permit-
+        brackets  (that is, when recursing), whereas any characters are permit-
         ted at the outer level.
           < (?: (?(R) \d++  | [^<>]*+) | (?R)) * >
-        In  this  pattern, (?(R) is the start of a conditional subpattern, with
+        In this pattern, (?(R) is the start of a conditional  subpattern,  with
-        two different alternatives for the recursive and  non-recursive  cases.
+        two  different  alternatives for the recursive and non-recursive cases.
         The (?R) item is the actual recursive call.
     Recursion difference from Perl
-        In  PCRE (like Python, but unlike Perl), a recursive subpattern call is
+        In PCRE (like Python, but unlike Perl), a recursive subpattern call  is
         always treated as an atomic group. That is, once it has matched some of
         the subject string, it is never re-entered, even if it contains untried
-        alternatives and there is a subsequent matching failure.  This  can  be
+        alternatives  and  there  is a subsequent matching failure. This can be
-        illustrated  by the following pattern, which purports to match a palin-
+        illustrated by the following pattern, which purports to match a  palin-
-        dromic string that contains an odd number of characters  (for  example,
+        dromic  string  that contains an odd number of characters (for example,
         "a", "aba", "abcba", "abcdcba"):
           ^(.|(.)(?1)\2)$
         The idea is that it either matches a single character, or two identical
-        characters surrounding a sub-palindrome. In Perl, this  pattern  works;
+        characters  surrounding  a sub-palindrome. In Perl, this pattern works;
-        in  PCRE  it  does  not if the pattern is longer than three characters.
+        in PCRE it does not if the pattern is  longer  than  three  characters.
         Consider the subject string "abcba":
-        At the top level, the first character is matched, but as it is  not  at
+        At  the  top level, the first character is matched, but as it is not at
         the end of the string, the first alternative fails; the second alterna-
         tive is taken and the recursion kicks in. The recursive call to subpat-
-        tern  1  successfully  matches the next character ("b"). (Note that the
+        tern 1 successfully matches the next character ("b").  (Note  that  the
         beginning and end of line tests are not part of the recursion).
-        Back at the top level, the next character ("c") is compared  with  what
+        Back  at  the top level, the next character ("c") is compared with what
-        subpattern  2 matched, which was "a". This fails. Because the recursion
+        subpattern 2 matched, which was "a". This fails. Because the  recursion
-        is treated as an atomic group, there are now  no  backtracking  points,
+        is  treated  as  an atomic group, there are now no backtracking points,
-        and  so  the  entire  match fails. (Perl is able, at this point, to re-
+        and so the entire match fails. (Perl is able, at  this  point,  to  re-
-        enter the recursion and try the second alternative.)  However,  if  the
+        enter  the  recursion  and try the second alternative.) However, if the
         pattern is written with the alternatives in the other order, things are
         different:
           ^((.)(?1)\2|.)$
-        This time, the recursing alternative is tried first, and  continues  to
+        This  time,  the recursing alternative is tried first, and continues to
-        recurse  until  it runs out of characters, at which point the recursion
+        recurse until it runs out of characters, at which point  the  recursion
-        fails. But this time we do have  another  alternative  to  try  at  the
+        fails.  But  this  time  we  do  have another alternative to try at the
-        higher  level.  That  is  the  big difference: in the previous case the
+        higher level. That is the big difference:  in  the  previous  case  the
         remaining alternative is at a deeper recursion level, which PCRE cannot
         use.
         To change the pattern so that matches all palindromic strings, not just
-        those with an odd number of characters, it is tempting  to  change  the
+        those  with  an  odd number of characters, it is tempting to change the
         pattern to this:
           ^((.)(?1)\2|.?)$
-        Again,  this  works  in Perl, but not in PCRE, and for the same reason.
+        Again, this works in Perl, but not in PCRE, and for  the  same  reason.
-        When a deeper recursion has matched a single character,  it  cannot  be
+        When  a  deeper  recursion has matched a single character, it cannot be
-        entered  again  in  order  to match an empty string. The solution is to
+        entered again in order to match an empty string.  The  solution  is  to
-        separate the two cases, and write out the odd and even cases as  alter-
+        separate  the two cases, and write out the odd and even cases as alter-
         natives at the higher level:
           ^(?:((.)(?1)\2|)|((.)(?3)\4|.))
-        If  you  want  to match typical palindromic phrases, the pattern has to
+        If you want to match typical palindromic phrases, the  pattern  has  to
         ignore all non-word characters, which can be done like this:
           ^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$
         If run with the PCRE_CASELESS option, this pattern matches phrases such
         as "A man, a plan, a canal: Panama!" and it works well in both PCRE and
-        Perl. Note the use of the possessive quantifier *+ to avoid  backtrack-
+        Perl.  Note the use of the possessive quantifier *+ to avoid backtrack-
-        ing  into  sequences of non-word characters. Without this, PCRE takes a
+        ing into sequences of non-word characters. Without this, PCRE  takes  a
-        great deal longer (ten times or more) to  match  typical  phrases,  and
+        great  deal  longer  (ten  times or more) to match typical phrases, and
         Perl takes so long that you think it has gone into a loop.
-        WARNING:  The  palindrome-matching patterns above work only if the sub-
+        WARNING: The palindrome-matching patterns above work only if  the  sub-
-        ject string does not start with a palindrome that is shorter  than  the
+        ject  string  does not start with a palindrome that is shorter than the
-        entire  string.  For example, although "abcba" is correctly matched, if
+        entire string.  For example, although "abcba" is correctly matched,  if
-        the subject is "ababa", PCRE finds the palindrome "aba" at  the  start,
+        the  subject  is "ababa", PCRE finds the palindrome "aba" at the start,
-        then  fails at top level because the end of the string does not follow.
+        then fails at top level because the end of the string does not  follow.
-        Once again, it cannot jump back into the recursion to try other  alter-
+        Once  again, it cannot jump back into the recursion to try other alter-
         natives, so the entire match fails.
  SUBPATTERNS AS SUBROUTINES
         If the syntax for a recursive subpattern reference (either by number or
-        by name) is used outside the parentheses to which it refers,  it  oper-
+        by  name)  is used outside the parentheses to which it refers, it oper-
-        ates  like a subroutine in a programming language. The "called" subpat-
+        ates like a subroutine in a programming language. The "called"  subpat-
         tern may be defined before or after the reference. A numbered reference
         can be absolute or relative, as in these examples:
-Line 5031 
 SUBPATTERNS AS SUBROUTINES
+Line 5040 
 SUBPATTERNS AS SUBROUTINES
           (sens|respons)e and \1ibility
-        matches  "sense and sensibility" and "response and responsibility", but
+        matches "sense and sensibility" and "response and responsibility",  but
         not "sense and responsibility". If instead the pattern
           (sens|respons)e and (?1)ibility
-        is used, it does match "sense and responsibility" as well as the  other
+        is  used, it does match "sense and responsibility" as well as the other
-        two  strings.  Another  example  is  given  in the discussion of DEFINE
+        two strings. Another example is  given  in  the  discussion  of  DEFINE
         above.
-        Like recursive subpatterns, a subroutine call is always treated  as  an
+        Like  recursive  subpatterns, a subroutine call is always treated as an
-        atomic  group. That is, once it has matched some of the subject string,
+        atomic group. That is, once it has matched some of the subject  string,
-        it is never re-entered, even if it contains  untried  alternatives  and
+        it  is  never  re-entered, even if it contains untried alternatives and
-        there  is a subsequent matching failure. Any capturing parentheses that
+        there is a subsequent matching failure. Any capturing parentheses  that
-        are set during the subroutine call  revert  to  their  previous  values
+        are  set  during  the  subroutine  call revert to their previous values
         afterwards.
-        When  a  subpattern is used as a subroutine, processing options such as
+        When a subpattern is used as a subroutine, processing options  such  as
         case-independence are fixed when the subpattern is defined. They cannot
         be changed for different calls. For example, consider this pattern:
           (abc)(?i:(?-1))
-        It  matches  "abcabc". It does not match "abcABC" because the change of
+        It matches "abcabc". It does not match "abcABC" because the  change  of
         processing option does not affect the called subpattern.
  ONIGURUMA SUBROUTINE SYNTAX
-        For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
+        For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
         name or a number enclosed either in angle brackets or single quotes, is
-        an alternative syntax for referencing a  subpattern  as  a  subroutine,
+        an  alternative  syntax  for  referencing a subpattern as a subroutine,
-        possibly  recursively. Here are two of the examples used above, rewrit-
+        possibly recursively. Here are two of the examples used above,  rewrit-
         ten using this syntax:
           (?<pn> \( ( (?>[^()]+) | \g<pn> )* \) )
           (sens|respons)e and \g'1'ibility
-        PCRE supports an extension to Oniguruma: if a number is preceded  by  a
+        PCRE  supports  an extension to Oniguruma: if a number is preceded by a
         plus or a minus sign it is taken as a relative reference. For example:
           (abc)(?i:\g<-1>)
-        Note  that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not
+        Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are  not
-        synonymous. The former is a back reference; the latter is a  subroutine
+        synonymous.  The former is a back reference; the latter is a subroutine
         call.
  CALLOUTS
         Perl has a feature whereby using the sequence (?{...}) causes arbitrary
-        Perl code to be obeyed in the middle of matching a regular  expression.
+        Perl  code to be obeyed in the middle of matching a regular expression.
         This makes it possible, amongst other things, to extract different sub-
         strings that match the same pair of parentheses when there is a repeti-
         tion.
         PCRE provides a similar feature, but of course it cannot obey arbitrary
         Perl code. The feature is called "callout". The caller of PCRE provides
-        an  external function by putting its entry point in the global variable
+        an external function by putting its entry point in the global  variable
-        pcre_callout.  By default, this variable contains NULL, which  disables
+        pcre_callout.   By default, this variable contains NULL, which disables
         all calling out.
-        Within  a  regular  expression,  (?C) indicates the points at which the
+        Within a regular expression, (?C) indicates the  points  at  which  the
-        external function is to be called. If you want  to  identify  different
+        external  function  is  to be called. If you want to identify different
-        callout  points, you can put a number less than 256 after the letter C.
+        callout points, you can put a number less than 256 after the letter  C.
-        The default value is zero.  For example, this pattern has  two  callout
+        The  default  value is zero.  For example, this pattern has two callout
         points:
           (?C1)abc(?C2)def
         If the PCRE_AUTO_CALLOUT flag is passed to pcre_compile(), callouts are
-        automatically installed before each item in the pattern. They  are  all
+        automatically  installed  before each item in the pattern. They are all
         numbered 255.
         During matching, when PCRE reaches a callout point (and pcre_callout is
-        set), the external function is called. It is provided with  the  number
+        set),  the  external function is called. It is provided with the number
-        of  the callout, the position in the pattern, and, optionally, one item
+        of the callout, the position in the pattern, and, optionally, one  item
-        of data originally supplied by the caller of pcre_exec().  The  callout
+        of  data  originally supplied by the caller of pcre_exec(). The callout
-        function  may cause matching to proceed, to backtrack, or to fail alto-
+        function may cause matching to proceed, to backtrack, or to fail  alto-
         gether. A complete description of the interface to the callout function
         is given in the pcrecallout documentation.
  BACKTRACKING CONTROL
-        Perl  5.10 introduced a number of "Special Backtracking Control Verbs",
+        Perl 5.10 introduced a number of "Special Backtracking Control  Verbs",
         which are described in the Perl documentation as "experimental and sub-
-        ject  to  change or removal in a future version of Perl". It goes on to
+        ject to change or removal in a future version of Perl". It goes  on  to
-        say: "Their usage in production code should be noted to avoid  problems
+        say:  "Their usage in production code should be noted to avoid problems
         during upgrades." The same remarks apply to the PCRE features described
         in this section.
-        Since these verbs are specifically related  to  backtracking,  most  of
+        Since  these  verbs  are  specifically related to backtracking, most of
-        them  can  be  used  only  when  the  pattern  is  to  be matched using
+        them can be  used  only  when  the  pattern  is  to  be  matched  using
         pcre_exec(), which uses a backtracking algorithm. With the exception of
         (*FAIL), which behaves like a failing negative assertion, they cause an
         error if encountered by pcre_dfa_exec().
         If any of these verbs are used in an assertion or subroutine subpattern
-        (including  recursive  subpatterns),  their  effect is confined to that
+        (including recursive subpatterns), their effect  is  confined  to  that
-        subpattern; it does not extend to the surrounding  pattern.  Note  that
+        subpattern;  it  does  not extend to the surrounding pattern. Note that
-        such  subpatterns are processed as anchored at the point where they are
+        such subpatterns are processed as anchored at the point where they  are
         tested.
-        The new verbs make use of what was previously invalid syntax: an  open-
+        The  new verbs make use of what was previously invalid syntax: an open-
         ing parenthesis followed by an asterisk. In Perl, they are generally of
         the form (*VERB:ARG) but PCRE does not support the use of arguments, so
-        its  general  form is just (*VERB). Any number of these verbs may occur
+        its general form is just (*VERB). Any number of these verbs  may  occur
         in a pattern. There are two kinds:
     Verbs that act immediately
-Line 5146 
 BACKTRACKING CONTROL
+Line 5155 
 BACKTRACKING CONTROL
            (*ACCEPT)
-        This verb causes the match to end successfully, skipping the  remainder
+        This  verb causes the match to end successfully, skipping the remainder
-        of  the pattern. When inside a recursion, only the innermost pattern is
+        of the pattern. When inside a recursion, only the innermost pattern  is
-        ended immediately. If (*ACCEPT) is inside  capturing  parentheses,  the
+        ended  immediately.  If  (*ACCEPT) is inside capturing parentheses, the
-        data  so  far  is  captured. (This feature was added to PCRE at release
+        data so far is captured. (This feature was added  to  PCRE  at  release
 .00.) For example:
           A((?:A|B(*ACCEPT)|C)D)
-        This matches "AB", "AAD", or "ACD"; when it matches "AB", "B"  is  cap-
+        This  matches  "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-
         tured by the outer parentheses.
           (*FAIL) or (*F)
-        This  verb  causes the match to fail, forcing backtracking to occur. It
+        This verb causes the match to fail, forcing backtracking to  occur.  It
-        is equivalent to (?!) but easier to read. The Perl documentation  notes
+        is  equivalent to (?!) but easier to read. The Perl documentation notes
-        that  it  is  probably  useful only when combined with (?{}) or (??{}).
+        that it is probably useful only when combined  with  (?{})  or  (??{}).
-        Those are, of course, Perl features that are not present in  PCRE.  The
+        Those  are,  of course, Perl features that are not present in PCRE. The
-        nearest  equivalent is the callout feature, as for example in this pat-
+        nearest equivalent is the callout feature, as for example in this  pat-
         tern:
           a+(?C)(*FAIL)
-        A match with the string "aaaa" always fails, but the callout  is  taken
+        A  match  with the string "aaaa" always fails, but the callout is taken
         before each backtrack happens (in this example, 10 times).
     Verbs that act after backtracking
         The following verbs do nothing when they are encountered. Matching con-
-        tinues with what follows, but if there is no subsequent match, a  fail-
+        tinues  with what follows, but if there is no subsequent match, a fail-
-        ure  is  forced.   The  verbs  differ  in  exactly what kind of failure
+        ure is forced.  The verbs  differ  in  exactly  what  kind  of  failure
         occurs.
           (*COMMIT)
-        This verb causes the whole match to fail outright if the  rest  of  the
+        This  verb  causes  the whole match to fail outright if the rest of the
-        pattern  does  not match. Even if the pattern is unanchored, no further
+        pattern does not match. Even if the pattern is unanchored,  no  further
-        attempts to find a match by advancing the starting  point  take  place.
+        attempts  to  find  a match by advancing the starting point take place.
-        Once  (*COMMIT)  has been passed, pcre_exec() is committed to finding a
+        Once (*COMMIT) has been passed, pcre_exec() is committed to  finding  a
         match at the current starting point, or not at all. For example:
           a+(*COMMIT)b
-        This matches "xxaab" but not "aacaab". It can be thought of as  a  kind
+        This  matches  "xxaab" but not "aacaab". It can be thought of as a kind
         of dynamic anchor, or "I've started, so I must finish."
           (*PRUNE)
-        This  verb causes the match to fail at the current position if the rest
+        This verb causes the match to fail at the current position if the  rest
         of the pattern does not match. If the pattern is unanchored, the normal
-        "bumpalong"  advance to the next starting character then happens. Back-
+        "bumpalong" advance to the next starting character then happens.  Back-
-        tracking can occur as usual to the left of (*PRUNE), or  when  matching
+        tracking  can  occur as usual to the left of (*PRUNE), or when matching
-        to  the right of (*PRUNE), but if there is no match to the right, back-
+        to the right of (*PRUNE), but if there is no match to the right,  back-
-        tracking cannot cross (*PRUNE).  In simple cases, the use  of  (*PRUNE)
+        tracking  cannot  cross (*PRUNE).  In simple cases, the use of (*PRUNE)
         is just an alternative to an atomic group or possessive quantifier, but
-        there are some uses of (*PRUNE) that cannot be expressed in  any  other
+        there  are  some uses of (*PRUNE) that cannot be expressed in any other
         way.
           (*SKIP)
-        This  verb  is like (*PRUNE), except that if the pattern is unanchored,
+        This verb is like (*PRUNE), except that if the pattern  is  unanchored,
-        the "bumpalong" advance is not to the next character, but to the  posi-
+        the  "bumpalong" advance is not to the next character, but to the posi-
-        tion  in  the  subject where (*SKIP) was encountered. (*SKIP) signifies
+        tion in the subject where (*SKIP) was  encountered.  (*SKIP)  signifies
-        that whatever text was matched leading up to it cannot  be  part  of  a
+        that  whatever  text  was  matched leading up to it cannot be part of a
         successful match. Consider:
           a+(*SKIP)b
-        If  the  subject  is  "aaaac...",  after  the first match attempt fails
+        If the subject is "aaaac...",  after  the  first  match  attempt  fails
-        (starting at the first character in the  string),  the  starting  point
+        (starting  at  the  first  character in the string), the starting point
         skips on to start the next attempt at "c". Note that a possessive quan-
-        tifer does not have the same effect as this example; although it  would
+        tifer  does not have the same effect as this example; although it would
-        suppress  backtracking  during  the  first  match  attempt,  the second
+        suppress backtracking  during  the  first  match  attempt,  the  second
-        attempt would start at the second character instead of skipping  on  to
+        attempt  would  start at the second character instead of skipping on to
         "c".
           (*THEN)
         This verb causes a skip to the next alternation if the rest of the pat-
         tern does not match. That is, it cancels pending backtracking, but only
-        within  the  current  alternation.  Its name comes from the observation
+        within the current alternation. Its name  comes  from  the  observation
         that it can be used for a pattern-based if-then-else block:
           ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
-        If the COND1 pattern matches, FOO is tried (and possibly further  items
+        If  the COND1 pattern matches, FOO is tried (and possibly further items
-        after  the  end  of  the group if FOO succeeds); on failure the matcher
+        after the end of the group if FOO succeeds);  on  failure  the  matcher
-        skips to the second alternative and tries COND2,  without  backtracking
+        skips  to  the second alternative and tries COND2, without backtracking
-        into  COND1.  If  (*THEN)  is  used outside of any alternation, it acts
+        into COND1. If (*THEN) is used outside  of  any  alternation,  it  acts
         exactly like (*PRUNE).
-Line 5251 
 AUTHOR
+Line 5260 
 AUTHOR
  REVISION
-        Last updated: 11 January 2010
+        Last updated: 06 March 2010
         Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 5363 
 GENERAL CATEGORY PROPERTY CODES FOR \p a
+Line 5372 
 GENERAL CATEGORY PROPERTY CODES FOR \p a
  SCRIPT NAMES FOR \p AND \P
-        Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
+        Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
-        Buhid, Canadian_Aboriginal, Carian, Cham, Cherokee, Common, Coptic, Cu-
+        Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
-        neiform,  Cypriot,  Cyrillic,  Deseret, Devanagari, Ethiopic, Georgian,
+        Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
-        Glagolitic, Gothic, Greek, Gujarati, Gurmukhi,  Han,  Hangul,  Hanunoo,
+        tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
-        Hebrew,  Hiragana,  Inherited, Kannada, Katakana, Kayah_Li, Kharoshthi,
+        Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
-        Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lycian, Lydian,  Malayalam,
+        rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
-        Mongolian,  Myanmar,  New_Tai_Lue, Nko, Ogham, Old_Italic, Old_Persian,
+        Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
-        Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Saurash-
+        Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
-        tra,  Shavian,  Sinhala,  Sudanese, Syloti_Nagri, Syriac, Tagalog, Tag-
+        Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
-        banwa,  Tai_Le,  Tamil,  Telugu,  Thaana,  Thai,   Tibetan,   Tifinagh,
+        Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
+        Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
+        Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
+        Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
         Ugaritic, Vai, Yi.
-Line 5552 
 BACKTRACKING CONTROL
+Line 5564 
 BACKTRACKING CONTROL
           (*ACCEPT)       force successful match
           (*FAIL)         force backtrack; synonym (*F)
-        The  following  act only when a subsequent match failure causes a back-
+        The following act only when a subsequent match failure causes  a  back-
         track to reach them. They all force a match failure, but they differ in
         what happens afterwards. Those that advance the start-of-match point do
         so only if the pattern is not anchored.
-Line 5565 
 BACKTRACKING CONTROL
+Line 5577 
 BACKTRACKING CONTROL
  NEWLINE CONVENTIONS
-        These are recognized only at the very start of the pattern or  after  a
+        These  are  recognized only at the very start of the pattern or after a
         (*BSR_...) or (*UTF8) option.
           (*CR)           carriage return only
-Line 5577 
 NEWLINE CONVENTIONS
+Line 5589 
 NEWLINE CONVENTIONS
  WHAT \R MATCHES
-        These  are  recognized only at the very start of the pattern or after a
+        These are recognized only at the very start of the pattern or  after  a
         (*...) option that sets the newline convention or UTF-8 mode.
           (*BSR_ANYCRLF)  CR, LF, or CRLF
-Line 5604 
 AUTHOR
+Line 5616 
 AUTHOR
  REVISION
-        Last updated: 11 April 2009
+        Last updated: 01 March 2010
-        Copyright (c) 1997-2009 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 6129 
 PCRE PERFORMANCE
+Line 6141 
 PCRE PERFORMANCE
         can affect both of them.
- MEMORY USAGE
+ COMPILED PATTERN MEMORY USAGE
         Patterns are compiled by PCRE into a reasonably efficient byte code, so
         that most simple patterns do not use much memory. However, there is one
-        case where memory usage can be unexpectedly large. When a parenthesized
+        case  where  the memory usage of a compiled pattern can be unexpectedly
-        subpattern has a quantifier with a minimum greater than 1 and/or a lim-
+        large. If a parenthesized subpattern has a quantifier  with  a  minimum
-        ited  maximum,  the  whole subpattern is repeated in the compiled code.
+        greater  than  1  and/or  a  limited  maximum,  the whole subpattern is
-        For example, the pattern
+        repeated in the compiled code. For example, the pattern
           (abc|def){2,4}
-Line 6178 
 MEMORY USAGE
+Line 6190 
 MEMORY USAGE
         otherwise handle.
+ STACK USAGE AT RUN TIME
+        When  pcre_exec()  is  used  for matching, certain kinds of pattern can
+        cause it to use large amounts of the process stack.  In  some  environ-
+        ments  the default process stack is quite small, and if it runs out the
+        result is often SIGSEGV.  This issue is probably  the  most  frequently
+        raised  problem  with  PCRE. Rewriting your pattern can often help. The
+        pcrestack documentation discusses this issue in detail.
  PROCESSING TIME
-        Certain  items  in regular expression patterns are processed more effi-
+        Certain items in regular expression patterns are processed  more  effi-
         ciently than others. It is more efficient to use a character class like
-        [aeiou]   than   a   set   of  single-character  alternatives  such  as
+        [aeiou]  than  a  set  of   single-character   alternatives   such   as
-        (a|e|i|o|u). In general, the simplest construction  that  provides  the
+        (a|e|i|o|u).  In  general,  the simplest construction that provides the
         required behaviour is usually the most efficient. Jeffrey Friedl's book
-        contains a lot of useful general discussion  about  optimizing  regular
+        contains  a  lot  of useful general discussion about optimizing regular
-        expressions  for  efficient  performance.  This document contains a few
+        expressions for efficient performance. This  document  contains  a  few
         observations about PCRE.
-        Using Unicode character properties (the \p,  \P,  and  \X  escapes)  is
+        Using  Unicode  character  properties  (the  \p, \P, and \X escapes) is
-        slow,  because PCRE has to scan a structure that contains data for over
+        slow, because PCRE has to scan a structure that contains data for  over
-        fifteen thousand characters whenever it needs a  character's  property.
+        fifteen  thousand  characters whenever it needs a character's property.
-        If  you  can  find  an  alternative pattern that does not use character
+        If you can find an alternative pattern  that  does  not  use  character
         properties, it will probably be faster.
-        When a pattern begins with .* not in  parentheses,  or  in  parentheses
+        When  a  pattern  begins  with .* not in parentheses, or in parentheses
         that are not the subject of a backreference, and the PCRE_DOTALL option
-        is set, the pattern is implicitly anchored by PCRE, since it can  match
+        is  set, the pattern is implicitly anchored by PCRE, since it can match
-        only  at  the start of a subject string. However, if PCRE_DOTALL is not
+        only at the start of a subject string. However, if PCRE_DOTALL  is  not
-        set, PCRE cannot make this optimization, because  the  .  metacharacter
+        set,  PCRE  cannot  make this optimization, because the . metacharacter
-        does  not then match a newline, and if the subject string contains new-
+        does not then match a newline, and if the subject string contains  new-
-        lines, the pattern may match from the character  immediately  following
+        lines,  the  pattern may match from the character immediately following
         one of them instead of from the very start. For example, the pattern
           .*second
-        matches  the subject "first\nand second" (where \n stands for a newline
+        matches the subject "first\nand second" (where \n stands for a  newline
-        character), with the match starting at the seventh character. In  order
+        character),  with the match starting at the seventh character. In order
         to do this, PCRE has to retry the match starting after every newline in
         the subject.
-        If you are using such a pattern with subject strings that do  not  con-
+        If  you  are using such a pattern with subject strings that do not con-
         tain newlines, the best performance is obtained by setting PCRE_DOTALL,
-        or starting the pattern with ^.* or ^.*? to indicate  explicit  anchor-
+        or  starting  the pattern with ^.* or ^.*? to indicate explicit anchor-
-        ing.  That saves PCRE from having to scan along the subject looking for
+        ing. That saves PCRE from having to scan along the subject looking  for
         a newline to restart at.
-        Beware of patterns that contain nested indefinite  repeats.  These  can
+        Beware  of  patterns  that contain nested indefinite repeats. These can
-        take  a  long time to run when applied to a string that does not match.
+        take a long time to run when applied to a string that does  not  match.
         Consider the pattern fragment
           ^(a+)*
-        This can match "aaaa" in 16 different ways, and this  number  increases
+        This  can  match "aaaa" in 16 different ways, and this number increases
-        very  rapidly  as the string gets longer. (The * repeat can match 0, 1,
+        very rapidly as the string gets longer. (The * repeat can match  0,  1,
-, 3, or 4 times, and for each of those cases other than 0 or 4, the  +
+,  3, or 4 times, and for each of those cases other than 0 or 4, the +
-        repeats  can  match  different numbers of times.) When the remainder of
+        repeats can match different numbers of times.) When  the  remainder  of
         the pattern is such that the entire match is going to fail, PCRE has in
-        principle  to  try  every  possible  variation,  and  this  can take an
+        principle to try  every  possible  variation,  and  this  can  take  an
         extremely long time, even for relatively short strings.
         An optimization catches some of the more simple cases such as
           (a+)*b
-        where a literal character follows. Before  embarking  on  the  standard
+        where  a  literal  character  follows. Before embarking on the standard
-        matching  procedure,  PCRE checks that there is a "b" later in the sub-
+        matching procedure, PCRE checks that there is a "b" later in  the  sub-
-        ject string, and if there is not, it fails the match immediately.  How-
+        ject  string, and if there is not, it fails the match immediately. How-
-        ever,  when  there  is no following literal this optimization cannot be
+        ever, when there is no following literal this  optimization  cannot  be
         used. You can see the difference by comparing the behaviour of
           (a+)*\d
-        with the pattern above. The former gives  a  failure  almost  instantly
+        with  the  pattern  above.  The former gives a failure almost instantly
-        when  applied  to  a  whole  line of "a" characters, whereas the latter
+        when applied to a whole line of  "a"  characters,  whereas  the  latter
         takes an appreciable time with strings longer than about 20 characters.
         In many cases, the solution to this kind of performance issue is to use
-Line 6260 
 AUTHOR
+Line 6282 
 AUTHOR
  REVISION
-        Last updated: 06 March 2007
+        Last updated: 07 March 2010
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------

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