This page describes the syntax of regular expressions in Perl. For a
description of how to I<use> regular expressions in matching
-operations, plus various examples of the same, see C<m//> and C<s///> in
-L<perlop>.
+operations, plus various examples of the same, see discussion
+of C<m//>, C<s///>, and C<??> in L<perlop/Regexp Quote-Like Operators>.
The matching operations can have various modifiers. The modifiers
-which relate to the interpretation of the regular expression inside
-are listed below. For the modifiers that alter the behaviour of the
-operation, see L<perlop/"m//"> and L<perlop/"s//">.
+that relate to the interpretation of the regular expression inside
+are listed below. For the modifiers that alter the way regular expression
+is used by Perl, see L<perlop/Regexp Quote-Like Operators>.
=over 4
If C<use locale> is in effect, the case map is taken from the current
locale. See L<perllocale>.
-=item m
+=item m
Treat string as multiple lines. That is, change "^" and "$" from matching
at only the very start or end of the string to the start or end of any
line anywhere within the string,
-=item s
+=item s
Treat string as single line. That is, change "." to match any character
whatsoever, even a newline, which it normally would not match.
-=item x
+The C</s> and C</m> modifiers both override the C<$*> setting. That is, no matter
+what C<$*> contains, C</s> without C</m> will force "^" to match only at the
+beginning of the string and "$" to match only at the end (or just before a
+newline at the end) of the string. Together, as /ms, they let the "." match
+any character whatsoever, while yet allowing "^" and "$" to match,
+respectively, just after and just before newlines within the string.
+
+=item x
Extend your pattern's legibility by permitting whitespace and comments.
the regular expression parser to ignore whitespace that is neither
backslashed nor within a character class. You can use this to break up
your regular expression into (slightly) more readable parts. The C<#>
-character is also treated as a meta-character introducing a comment,
+character is also treated as a metacharacter introducing a comment,
just as in ordinary Perl code. This also means that if you want real
-whitespace or C<#> characters in the pattern that you'll have to either
+whitespace or C<#> characters in the pattern (outside of a character
+class, where they are unaffected by C</x>), that you'll either have to
escape them or encode them using octal or hex escapes. Taken together,
these features go a long way towards making Perl's regular expressions
-more readable. See the C comment deletion code in L<perlop>.
+more readable. Note that you have to be careful not to include the
+pattern delimiter in the comment--perl has no way of knowing you did
+not intend to close the pattern early. See the C-comment deletion code
+in L<perlop>.
=head2 Regular Expressions
The patterns used in pattern matching are regular expressions such as
-those supplied in the Version 8 regexp routines. (In fact, the
+those supplied in the Version 8 regex routines. (In fact, the
routines are derived (distantly) from Henry Spencer's freely
redistributable reimplementation of the V8 routines.)
See L<Version 8 Regular Expressions> for details.
In particular the following metacharacters have their standard I<egrep>-ish
meanings:
- \ Quote the next meta-character
+ \ Quote the next metacharacter
^ Match the beginning of the line
. Match any character (except newline)
$ Match the end of the line (or before newline at the end)
modifier to C<{1,}>, and the "?" modifier to C<{0,1}>. n and m are limited
to integral values less than 65536.
-By default, a quantified sub-pattern is "greedy", that is, it will match as
-many times as possible without causing the rest of the pattern not to match.
-The standard quantifiers are all "greedy", in that they match as many
-occurrences as possible (given a particular starting location) without
-causing the pattern to fail. If you want it to match the minimum number
-of times possible, follow the quantifier with a "?" after any of them.
-Note that the meanings don't change, just the "gravity":
+By default, a quantified subpattern is "greedy", that is, it will match as
+many times as possible (given a particular starting location) while still
+allowing the rest of the pattern to match. If you want it to match the
+minimum number of times possible, follow the quantifier with a "?". Note
+that the meanings don't change, just the "greediness":
*? Match 0 or more times
+? Match 1 or more times
\L lowercase till \E (think vi)
\U uppercase till \E (think vi)
\E end case modification (think vi)
- \Q quote regexp metacharacters till \E
+ \Q quote (disable) pattern metacharacters till \E
If C<use locale> is in effect, the case map used by C<\l>, C<\L>, C<\u>
-and <\U> is taken from the current locale. See L<perllocale>.
+and C<\U> is taken from the current locale. See L<perllocale>.
+
+You cannot include a literal C<$> or C<@> within a C<\Q> sequence.
+An unescaped C<$> or C<@> interpolates the corresponding variable,
+while escaping will cause the literal string C<\$> to be matched.
+You'll need to write something like C<m/\Quser\E\@\Qhost/>.
In addition, Perl defines the following:
\d Match a digit character
\D Match a non-digit character
-Note that C<\w> matches a single alphanumeric character, not a whole
+A C<\w> matches a single alphanumeric character, not a whole
word. To match a word you'd need to say C<\w+>. If C<use locale> is in
effect, the list of alphabetic characters generated by C<\w> is taken
from the current locale. See L<perllocale>. You may use C<\w>, C<\W>,
\b Match a word boundary
\B Match a non-(word boundary)
- \A Match at only beginning of string
- \Z Match at only end of string (or before newline at the end)
- \G Match only where previous m//g left off
+ \A Match only at beginning of string
+ \Z Match only at end of string, or before newline at the end
+ \z Match only at end of string
+ \G Match only where previous m//g left off (works only with /g)
A word boundary (C<\b>) is defined as a spot between two characters that
has a C<\w> on one side of it and a C<\W> on the other side of it (in
either order), counting the imaginary characters off the beginning and
end of the string as matching a C<\W>. (Within character classes C<\b>
represents backspace rather than a word boundary.) The C<\A> and C<\Z> are
-just like "^" and "$" except that they won't match multiple times when the
+just like "^" and "$", except that they won't match multiple times when the
C</m> modifier is used, while "^" and "$" will match at every internal line
boundary. To match the actual end of the string, not ignoring newline,
-you can use C<\Z(?!\n)>. The C<\G> assertion can be used to mix global
-matches (using C<m//g>) and non-global ones, as described in
+you can use C<\z>. The C<\G> assertion can be used to chain global
+matches (using C<m//g>), as described in
L<perlop/"Regexp Quote-Like Operators">.
+
It is also useful when writing C<lex>-like scanners, when you have several
-regexps which you want to match against consequent substrings of your
+patterns that you want to match against consequent substrings of your
string, see the previous reference.
The actual location where C<\G> will match can also be influenced
by using C<pos()> as an lvalue. See L<perlfunc/pos>.
the program, it has to provide them on each and every pattern match.
This can slow your program down. The same mechanism that handles
these provides for the use of $1, $2, etc., so you pay the same price
-for each regexp that contains capturing parentheses. But if you never
-use $&, etc., in your script, then regexps I<without> capturing
+for each pattern that contains capturing parentheses. But if you never
+use $&, etc., in your script, then patterns I<without> capturing
parentheses won't be penalized. So avoid $&, $', and $` if you can,
but if you can't (and some algorithms really appreciate them), once
you've used them once, use them at will, because you've already paid
-the price.
-
-You will note that all backslashed metacharacters in Perl are
-alphanumeric, such as C<\b>, C<\w>, C<\n>. Unlike some other regular expression
-languages, there are no backslashed symbols that aren't alphanumeric.
-So anything that looks like \\, \(, \), \E<lt>, \E<gt>, \{, or \} is always
-interpreted as a literal character, not a meta-character. This makes it
-simple to quote a string that you want to use for a pattern but that
-you are afraid might contain metacharacters. Quote simply all the
+the price. As of 5.005, $& is not so costly as the other two.
+
+Backslashed metacharacters in Perl are
+alphanumeric, such as C<\b>, C<\w>, C<\n>. Unlike some other regular
+expression languages, there are no backslashed symbols that aren't
+alphanumeric. So anything that looks like \\, \(, \), \E<lt>, \E<gt>,
+\{, or \} is always interpreted as a literal character, not a
+metacharacter. This was once used in a common idiom to disable or
+quote the special meanings of regular expression metacharacters in a
+string that you want to use for a pattern. Simply quote all
non-alphanumeric characters:
$pattern =~ s/(\W)/\\$1/g;
-You can also use the built-in quotemeta() function to do this.
-An even easier way to quote metacharacters right in the match operator
-is to say
+Now it is much more common to see either the quotemeta() function or
+the C<\Q> escape sequence used to disable all metacharacters' special
+meanings like this:
/$unquoted\Q$quoted\E$unquoted/
=over 10
-=item (?#text)
+=item C<(?#text)>
A comment. The text is ignored. If the C</x> switch is used to enable
-whitespace formatting, a simple C<#> will suffice.
+whitespace formatting, a simple C<#> will suffice. Note that perl closes
+the comment as soon as it sees a C<)>, so there is no way to put a literal
+C<)> in the comment.
-=item (?:regexp)
+=item C<(?:pattern)>
-This groups things like "()" but doesn't make backreferences like "()" does. So
+This is for clustering, not capturing; it groups subexpressions like
+"()", but doesn't make backreferences as "()" does. So
- split(/\b(?:a|b|c)\b/)
+ @fields = split(/\b(?:a|b|c)\b/)
is like
- split(/\b(a|b|c)\b/)
+ @fields = split(/\b(a|b|c)\b/)
but doesn't spit out extra fields.
-=item (?=regexp)
+=item C<(?=pattern)>
A zero-width positive lookahead assertion. For example, C</\w+(?=\t)/>
matches a word followed by a tab, without including the tab in C<$&>.
-=item (?!regexp)
+=item C<(?!pattern)>
A zero-width negative lookahead assertion. For example C</foo(?!bar)/>
matches any occurrence of "foo" that isn't followed by "bar". Note
however that lookahead and lookbehind are NOT the same thing. You cannot
-use this for lookbehind: C</(?!foo)bar/> will not find an occurrence of
-"bar" that is preceded by something which is not "foo". That's because
-the C<(?!foo)> is just saying that the next thing cannot be "foo"--and
-it's not, it's a "bar", so "foobar" will match. You would have to do
-something like C</(?!foo)...bar/> for that. We say "like" because there's
-the case of your "bar" not having three characters before it. You could
-cover that this way: C</(?:(?!foo)...|^..?)bar/>. Sometimes it's still
-easier just to say:
-
- if (/foo/ && $` =~ /bar$/)
-
-
-=item (?imsx)
+use this for lookbehind.
+
+If you are looking for a "bar" that isn't preceded by a "foo", C</(?!foo)bar/>
+will not do what you want. That's because the C<(?!foo)> is just saying that
+the next thing cannot be "foo"--and it's not, it's a "bar", so "foobar" will
+match. You would have to do something like C</(?!foo)...bar/> for that. We
+say "like" because there's the case of your "bar" not having three characters
+before it. You could cover that this way: C</(?:(?!foo)...|^.{0,2})bar/>.
+Sometimes it's still easier just to say:
+
+ if (/bar/ && $` !~ /foo$/)
+
+For lookbehind see below.
+
+=item C<(?E<lt>=pattern)>
+
+A zero-width positive lookbehind assertion. For example, C</(?E<lt>=\t)\w+/>
+matches a word following a tab, without including the tab in C<$&>.
+Works only for fixed-width lookbehind.
+
+=item C<(?<!pattern)>
+
+A zero-width negative lookbehind assertion. For example C</(?<!bar)foo/>
+matches any occurrence of "foo" that isn't following "bar".
+Works only for fixed-width lookbehind.
+
+=item C<(?{ code })>
+
+Experimental "evaluate any Perl code" zero-width assertion. Always
+succeeds. C<code> is not interpolated. Currently the rules to
+determine where the C<code> ends are somewhat convoluted.
+
+The C<code> is properly scoped in the following sense: if the assertion
+is backtracked (compare L<"Backtracking">), all the changes introduced after
+C<local>isation are undone, so
+
+ $_ = 'a' x 8;
+ m<
+ (?{ $cnt = 0 }) # Initialize $cnt.
+ (
+ a
+ (?{
+ local $cnt = $cnt + 1; # Update $cnt, backtracking-safe.
+ })
+ )*
+ aaaa
+ (?{ $res = $cnt }) # On success copy to non-localized
+ # location.
+ >x;
+
+will set C<$res = 4>. Note that after the match $cnt returns to the globally
+introduced value 0, since the scopes which restrict C<local> statements
+are unwound.
+
+This assertion may be used as L<C<(?(condition)yes-pattern|no-pattern)>>
+switch. If I<not> used in this way, the result of evaluation of C<code>
+is put into variable $^R. This happens immediately, so $^R can be used from
+other C<(?{ code })> assertions inside the same regular expression.
+
+The above assignment to $^R is properly localized, thus the old value of $^R
+is restored if the assertion is backtracked (compare L<"Backtracking">).
+
+B<WARNING>: This is a grave security risk for arbitrarily interpolated
+patterns. It introduces security holes in previously safe programs.
+A fix to Perl, and to this documentation, will be forthcoming prior
+to the actual 5.005 release.
+
+=item C<(?E<gt>pattern)>
+
+An "independent" subexpression. Matches the substring that a
+I<standalone> C<pattern> would match if anchored at the given position,
+B<and only this substring>.
+
+Say, C<^(?E<gt>a*)ab> will never match, since C<(?E<gt>a*)> (anchored
+at the beginning of string, as above) will match I<all> characters
+C<a> at the beginning of string, leaving no C<a> for C<ab> to match.
+In contrast, C<a*ab> will match the same as C<a+b>, since the match of
+the subgroup C<a*> is influenced by the following group C<ab> (see
+L<"Backtracking">). In particular, C<a*> inside C<a*ab> will match
+less characters that a standalone C<a*>, since this makes the tail match.
+
+An effect similar to C<(?E<gt>pattern)> may be achieved by
+
+ (?=(pattern))\1
+
+since the lookahead is in I<"logical"> context, thus matches the same
+substring as a standalone C<a+>. The following C<\1> eats the matched
+string, thus making a zero-length assertion into an analogue of
+C<(?>...)>. (The difference between these two constructs is that the
+second one uses a catching group, thus shifting ordinals of
+backreferences in the rest of a regular expression.)
+
+This construct is useful for optimizations of "eternal"
+matches, because it will not backtrack (see L<"Backtracking">).
+
+ m{ \( (
+ [^()]+
+ |
+ \( [^()]* \)
+ )+
+ \)
+ }x
+
+That will efficiently match a nonempty group with matching
+two-or-less-level-deep parentheses. However, if there is no such group,
+it will take virtually forever on a long string. That's because there are
+so many different ways to split a long string into several substrings.
+This is essentially what C<(.+)+> is doing, and this is a subpattern
+of the above pattern. Consider that C<((()aaaaaaaaaaaaaaaaaa> on the
+pattern above detects no-match in several seconds, but that each extra
+letter doubles this time. This exponential performance will make it
+appear that your program has hung.
+
+However, a tiny modification of this pattern
+
+ m{ \( (
+ (?> [^()]+ )
+ |
+ \( [^()]* \)
+ )+
+ \)
+ }x
+
+which uses C<(?E<gt>...)> matches exactly when the one above does (verifying
+this yourself would be a productive exercise), but finishes in a fourth
+the time when used on a similar string with 1000000 C<a>s. Be aware,
+however, that this pattern currently triggers a warning message under
+B<-w> saying it C<"matches the null string many times">):
+
+On simple groups, such as the pattern C<(?> [^()]+ )>, a comparable
+effect may be achieved by negative lookahead, as in C<[^()]+ (?! [^()] )>.
+This was only 4 times slower on a string with 1000000 C<a>s.
+
+=item C<(?(condition)yes-pattern|no-pattern)>
+
+=item C<(?(condition)yes-pattern)>
+
+Conditional expression. C<(condition)> should be either an integer in
+parentheses (which is valid if the corresponding pair of parentheses
+matched), or lookahead/lookbehind/evaluate zero-width assertion.
+
+Say,
+
+ m{ ( \( )?
+ [^()]+
+ (?(1) \) )
+ }x
+
+matches a chunk of non-parentheses, possibly included in parentheses
+themselves.
+
+=item C<(?imsx)>
One or more embedded pattern-match modifiers. This is particularly
useful for patterns that are specified in a table somewhere, some of
pattern. For example:
$pattern = "foobar";
- if ( /$pattern/i )
+ if ( /$pattern/i ) { }
# more flexible:
$pattern = "(?i)foobar";
- if ( /$pattern/ )
+ if ( /$pattern/ ) { }
+
+These modifiers are localized inside an enclosing group (if any). Say,
+
+ ( (?i) blah ) \s+ \1
+
+(assuming C<x> modifier, and no C<i> modifier outside of this group)
+will match a repeated (I<including the case>!) word C<blah> in any
+case.
=back
-The specific choice of question mark for this and the new minimal
-matching construct was because 1) question mark is pretty rare in older
-regular expressions, and 2) whenever you see one, you should stop
-and "question" exactly what is going on. That's psychology...
+A question mark was chosen for this and for the new minimal-matching
+construct because 1) question mark is pretty rare in older regular
+expressions, and 2) whenever you see one, you should stop and "question"
+exactly what is going on. That's psychology...
=head2 Backtracking
-A fundamental feature of regular expression matching involves the notion
-called I<backtracking>. which is used (when needed) by all regular
-expression quantifiers, namely C<*>, C<*?>, C<+>, C<+?>, C<{n,m}>, and
-C<{n,m}?>.
+A fundamental feature of regular expression matching involves the
+notion called I<backtracking>, which is currently used (when needed)
+by all regular expression quantifiers, namely C<*>, C<*?>, C<+>,
+C<+?>, C<{n,m}>, and C<{n,m}?>.
For a regular expression to match, the I<entire> regular expression must
match, not just part of it. So if the beginning of a pattern containing a
regular expression is merely a set of assertions that gives a definition
of success. There may be 0, 1, or several different ways that the
definition might succeed against a particular string. And if there are
-multiple ways it might succeed, you need to understand backtracking to know which variety of success you will achieve.
+multiple ways it might succeed, you need to understand backtracking to
+know which variety of success you will achieve.
When using lookahead assertions and negations, this can all get even
-tricker. Imagine you'd like to find a sequence of non-digits not
+tricker. Imagine you'd like to find a sequence of non-digits not
followed by "123". You might try to write that as
$_ = "ABC123";
that you've asked "Is it true that at the start of $x, following 0 or more
non-digits, you have something that's not 123?" If the pattern matcher had
let C<\D*> expand to "ABC", this would have caused the whole pattern to
-fail.
+fail.
The search engine will initially match C<\D*> with "ABC". Then it will
-try to match C<(?!123> with "123" which, of course, fails. But because
+try to match C<(?!123> with "123", which of course fails. But because
a quantifier (C<\D*>) has been used in the regular expression, the
search engine can backtrack and retry the match differently
-in the hope of matching the complete regular expression.
+in the hope of matching the complete regular expression.
-Well now,
-the pattern really, I<really> wants to succeed, so it uses the
-standard regexp back-off-and-retry and lets C<\D*> expand to just "AB" this
+The pattern really, I<really> wants to succeed, so it uses the
+standard pattern back-off-and-retry and lets C<\D*> expand to just "AB" this
time. Now there's indeed something following "AB" that is not
"123". It's in fact "C123", which suffices.
6: got ABC
-In other words, the two zero-width assertions next to each other work like
+In other words, the two zero-width assertions next to each other work as though
they're ANDed together, just as you'd use any builtin assertions: C</^$/>
matches only if you're at the beginning of the line AND the end of the
line simultaneously. The deeper underlying truth is that juxtaposition in
And if you used C<*>'s instead of limiting it to 0 through 5 matches, then
it would take literally forever--or until you ran out of stack space.
+A powerful tool for optimizing such beasts is "independent" groups,
+which do not backtrace (see L<C<(?E<gt>pattern)>>). Note also that
+zero-length lookahead/lookbehind assertions will not backtrace to make
+the tail match, since they are in "logical" context: only the fact
+whether they match or not is considered relevant. For an example
+where side-effects of a lookahead I<might> have influenced the
+following match, see L<C<(?E<gt>pattern)>>.
+
=head2 Version 8 Regular Expressions
-In case you're not familiar with the "regular" Version 8 regexp
+In case you're not familiar with the "regular" Version 8 regex
routines, here are the pattern-matching rules not described above.
-Any single character matches itself, unless it is a I<meta-character>
+Any single character matches itself, unless it is a I<metacharacter>
with a special meaning described here or above. You can cause
-characters which normally function as metacharacters to be interpreted
+characters that normally function as metacharacters to be interpreted
literally by prefixing them with a "\" (e.g., "\." matches a ".", not any
character; "\\" matches a "\"). A series of characters matches that
series of characters in the target string, so the pattern C<blurfl>
would match "blurfl" in the target string.
You can specify a character class, by enclosing a list of characters
-in C<[]>, which will match any one of the characters in the list. If the
+in C<[]>, which will match any one character from the list. If the
first character after the "[" is "^", the class matches any character not
in the list. Within a list, the "-" character is used to specify a
-range, so that C<a-z> represents all the characters between "a" and "z",
-inclusive.
-
-Characters may be specified using a meta-character syntax much like that
+range, so that C<a-z> represents all characters between "a" and "z",
+inclusive. If you want "-" itself to be a member of a class, put it
+at the start or end of the list, or escape it with a backslash. (The
+following all specify the same class of three characters: C<[-az]>,
+C<[az-]>, and C<[a\-z]>. All are different from C<[a-z]>, which
+specifies a class containing twenty-six characters.)
+
+Characters may be specified using a metacharacter syntax much like that
used in C: "\n" matches a newline, "\t" a tab, "\r" a carriage return,
"\f" a form feed, etc. More generally, \I<nnn>, where I<nnn> is a string
of octal digits, matches the character whose ASCII value is I<nnn>.
Similarly, \xI<nn>, where I<nn> are hexadecimal digits, matches the
character whose ASCII value is I<nn>. The expression \cI<x> matches the
-ASCII character control-I<x>. Finally, the "." meta-character matches any
+ASCII character control-I<x>. Finally, the "." metacharacter matches any
character except "\n" (unless you use C</s>).
You can specify a series of alternatives for a pattern using "|" to
separate them, so that C<fee|fie|foe> will match any of "fee", "fie",
-or "foe" in the target string (as would C<f(e|i|o)e>). Note that the
+or "foe" in the target string (as would C<f(e|i|o)e>). The
first alternative includes everything from the last pattern delimiter
("(", "[", or the beginning of the pattern) up to the first "|", and
the last alternative contains everything from the last "|" to the next
pattern delimiter. For this reason, it's common practice to include
alternatives in parentheses, to minimize confusion about where they
-start and end. Note however that "|" is interpreted as a literal with
-square brackets, so if you write C<[fee|fie|foe]> you're really only
-matching C<[feio|]>.
+start and end.
+
+Alternatives are tried from left to right, so the first
+alternative found for which the entire expression matches, is the one that
+is chosen. This means that alternatives are not necessarily greedy. For
+example: when mathing C<foo|foot> against "barefoot", only the "foo"
+part will match, as that is the first alternative tried, and it successfully
+matches the target string. (This might not seem important, but it is
+important when you are capturing matched text using parentheses.)
+
+Also remember that "|" is interpreted as a literal within square brackets,
+so if you write C<[fee|fie|foe]> you're really only matching C<[feio|]>.
-Within a pattern, you may designate sub-patterns for later reference by
+Within a pattern, you may designate subpatterns for later reference by
enclosing them in parentheses, and you may refer back to the I<n>th
-sub-pattern later in the pattern using the meta-character \I<n>.
-Sub-patterns are numbered based on the left to right order of their
-opening parenthesis. Note that a backreference matches whatever
-actually matched the sub-pattern in the string being examined, not the
-rules for that sub-pattern. Therefore, C<(0|0x)\d*\s\1\d*> will
-match "0x1234 0x4321",but not "0x1234 01234", because sub-pattern 1
+subpattern later in the pattern using the metacharacter \I<n>.
+Subpatterns are numbered based on the left to right order of their
+opening parenthesis. A backreference matches whatever
+actually matched the subpattern in the string being examined, not the
+rules for that subpattern. Therefore, C<(0|0x)\d*\s\1\d*> will
+match "0x1234 0x4321", but not "0x1234 01234", because subpattern 1
actually matched "0x", even though the rule C<0|0x> could
potentially match the leading 0 in the second number.
=head2 WARNING on \1 vs $1
-Some people get too used to writing things like
+Some people get too used to writing things like:
$pattern =~ s/(\W)/\\\1/g;
of doing that, you get yourself into trouble if you then add an C</e>
modifier.
- s/(\d+)/ \1 + 1 /eg;
+ s/(\d+)/ \1 + 1 /eg; # causes warning under -w
Or if you try to do
C<${1}000>. Basically, the operation of interpolation should not be confused
with the operation of matching a backreference. Certainly they mean two
different things on the I<left> side of the C<s///>.
+
+=head2 SEE ALSO
+
+L<perlop/"Regexp Quote-Like Operators">.
+
+L<perlfunc/pos>.
+
+L<perllocale>.
+
+I<Mastering Regular Expressions> (see L<perlbook>) by Jeffrey Friedl.
projects / p5sagit/p5-mst-13.2.git / blobdiff