X</m> X<regex, multiline> X<regexp, multiline> X<regular expression, multiline>
Treat string as multiple lines. That is, change "^" and "$" from matching
-the start or end of the string to matching the start or end of any
-line anywhere within the string.
+the start or end of line only at the left and right ends of the string to
+matching them anywhere within the string.
=item s
X</s> X<regex, single-line> X<regexp, single-line>
C<sS>, and C<ss>, otherwise not.
This modifier may be specified to be the default by C<use feature
-'unicode_strings> or C<L<use 5.012|perlfunc/use VERSION>> (or higher),
+'unicode_strings>, C<use locale ':not_characters'>, or
+C<L<use 5.012|perlfunc/use VERSION>> (or higher),
but see L</Which character set modifier is in effect?>.
X</u>
listed below that also change the defaults.
Otherwise, C<L<use locale|perllocale>> sets the default modifier to C</l>;
-and C<L<use feature 'unicode_strings|feature>> or
+and C<L<use feature 'unicode_strings|feature>>, or
C<L<use 5.012|perlfunc/use VERSION>> (or higher) set the default to
C</u> when not in the same scope as either C<L<use locale|perllocale>>
-or C<L<use bytes|bytes>>. Unlike the mechanisms mentioned above, these
+or C<L<use bytes|bytes>>.
+(C<L<use locale ':not_characters'|perllocale/Unicode and UTF-8>> also
+sets the default to C</u>, overriding any plain C<use locale>.)
+Unlike the mechanisms mentioned above, these
affect operations besides regular expressions pattern matching, and so
give more consistent results with other operators, including using
C<\U>, C<\l>, etc. in substitution replacements.
(If a curly bracket occurs in any other context and does not form part of
a backslashed sequence like C<\x{...}>, it is treated
-as a regular character. In particular, the lower bound
-is not optional.) The "*" quantifier is equivalent to C<{0,}>, the "+"
+as a regular character. In particular, the lower quantifier bound
+is not optional. However, in Perl v5.18, it is planned to issue a
+deprecation warning for all such occurrences, and in Perl v5.20 to
+require literal uses of a curly bracket to be escaped, say by preceding
+them with a backslash or enclosing them within square brackets, (C<"\{">
+or C<"[{]">). This change will allow for future syntax extensions (like
+making the lower bound of a quantifier optional), and better error
+checking of quantifiers. Now, a typo in a quantifier silently causes
+it to be treated as the literal characters. For example,
+
+ /o{4,3}/
+
+looks like a quantifier that matches 0 times, since 4 is greater than 3,
+but it really means to match the sequence of six characters
+S<C<"o { 4 , 3 }">>.)
+
+The "*" quantifier is equivalent to C<{0,}>, the "+"
quantifier to C<{1,}>, and the "?" quantifier to C<{0,1}>. n and m are limited
to non-negative integral values less than a preset limit defined when perl is built.
This is usually 32766 on the most common platforms. The actual limit can
I<need> to use literal backslashes within C<\Q...\E>,
consult L<perlop/"Gory details of parsing quoted constructs">.
+C<quotemeta()> and C<\Q> are fully described in L<perlfunc/quotemeta>.
+
=head2 Extended Patterns
Perl also defines a consistent extension syntax for features not
modifier outside this group.
These modifiers do not carry over into named subpatterns called in the
-enclosing group. In other words, a pattern such as C<((?i)(&NAME))> does not
+enclosing group. In other words, a pattern such as C<((?i)(?&NAME))> does not
change the case-sensitivity of the "NAME" pattern.
Any of these modifiers can be set to apply globally to all regular
if it were inserted instead of this construct. Note that this means
that the contents of capture groups defined inside an eval'ed pattern
are not available outside of the pattern, and vice versa, there is no
-way for the inner pattern to refer to a capture group defined outside.
-Thus,
+way for the inner pattern returned from the code block to refer to a
+capture group defined outside. (The code block itself can use C<$1>, etc.,
+to refer to the enclosing pattern's capture groups.) Thus,
('a' x 100)=~/(??{'(.)' x 100})/
https://perl5.git.perl.org / perl5.git / blobdiff