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

Diff of /code/trunk/doc/pcre.txt

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-revision 487 by ph10,
Wed Jan  6 10:26:55 2010 UTC
+revision 488 by ph10,
Mon Jan 11 15:29:42 2010 UTC
 Line 3246 
 BACKSLASH
           \n        linefeed (hex 0A)
           \r        carriage return (hex 0D)
           \t        tab (hex 09)
-          \ddd      character with octal code ddd, or backreference
+          \ddd      character with octal code ddd, or back reference
           \xhh      character with hex code hh
           \x{hhh..} character with hex code hhh..
 Line 4051 
 DUPLICATE SUBPATTERN NUMBERS
           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
           # 1            2         2  3        2     3     4
-        A  backreference  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
         matches "abcabc" or "defdef":
 Line 4085 
 NAMED SUBPATTERNS
         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
-        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
         by number.
 Line 4121 
 NAMED SUBPATTERNS
         that  name  that  matched.  This saves searching to find which numbered
         subpattern it was.
-        If you make a backreference to a non-unique named subpattern from else-
+        If you make a back reference to  a  non-unique  named  subpattern  from
-        where  in the pattern, the one that corresponds to the first occurrence
+        elsewhere  in the pattern, the one that corresponds to the first occur-
-        of the name is used. In the absence of duplicate numbers (see the  pre-
+        rence of the name is used. In the absence of duplicate numbers (see the
-        vious  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
         below),  either  to check whether a subpattern has matched, or to check
         for recursion, all subpatterns with the same name are  tested.  If  the
 Line 4270 
 REPETITION
         mization, or alternatively using ^ to indicate anchoring explicitly.
         However, there is one situation where the optimization cannot be  used.
-        When  .*   is  inside  capturing  parentheses that are the subject of a
+        When .*  is inside capturing parentheses that are the subject of a back
-        backreference elsewhere in the pattern, a match at the start  may  fail
+        reference elsewhere in the pattern, a match at the start may fail where
-        where a later one succeeds. Consider, for example:
+        a later one succeeds. Consider, for example:
           (.*)abc\1
 Line 4494 
 BACK REFERENCES
         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
         fails  when  the subpattern is first used, so, for example, (a\1) never
         matches.  However, such references can be useful inside  repeated  sub-
-Line 4508 
 BACK REFERENCES
+Line 4510 
 BACK REFERENCES
         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
+        treated  as  an atomic group.  Once the whole group has been matched, a
+        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 4537 
 ASSERTIONS
+Line 4544 
 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 4577 
 ASSERTIONS
+Line 4584 
 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 4641 
 ASSERTIONS
+Line 4648 
 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 4660 
 ASSERTIONS
+Line 4667 
 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 4757 
 CONDITIONAL SUBPATTERNS
+Line 4764 
 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 4837 
 RECURSIVE PATTERNS
+Line 4844 
 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 5024 
 SUBPATTERNS AS SUBROUTINES
+Line 5031 
 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 5139 
 BACKTRACKING CONTROL
+Line 5146 
 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 5244 
 AUTHOR
+Line 5251 
 AUTHOR
  REVISION
-        Last updated: 18 October 2009
+        Last updated: 11 January 2010
-        Copyright (c) 1997-2009 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------

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