diff options
Diffstat (limited to 'pod/perlre.pod')
| -rw-r--r-- | pod/perlre.pod | 40 |
1 files changed, 30 insertions, 10 deletions
diff --git a/pod/perlre.pod b/pod/perlre.pod index 55dc1209bc..c4dbac63c6 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -13,10 +13,28 @@ The matching operations can have various modifiers, some of which relate to the interpretation of the regular expression inside. These are: - i Do case-insensitive pattern matching. - m Treat string as multiple lines. - s Treat string as single line. - x Extend your pattern's legibility with whitespace and comments. +=over 4 + +=item i + +Do case-insensitive pattern matching. + +=item m + +Treat string as multiple lines. That is, change "^" and "$" from matching +only at the very start or end of the string to the start or end of any +line anywhere within the string, + +=item s + +Treat string as single line. That is, change "." to match any character +whatsoever, even a newline, which it normally would not match. + +=item x + +Extend your pattern's legibility by permitting whitespace and comments. + +=back These are usually written as "the C</x> modifier", even though the delimiter in question might not actually be a slash. In fact, any of these @@ -24,13 +42,15 @@ modifiers may also be embedded within the regular expression itself using the new C<(?...)> construct. See below. The C</x> modifier itself needs a little more explanation. It tells -the regular expression parser to ignore whitespace that is not -backslashed or within a character class. You can use this to break up +the regular expression parser to ignore whitespace that is neither +backslashed nor within a character class. You can use this to break up your regular expression into (slightly) more readable parts. The C<#> character is also treated as a metacharacter introducing a comment, -just as in ordinary Perl code. Taken together, these features go a -long way towards making Perl 5 a readable language. See the C comment -deletion code in L<perlop>. +just as in ordinary Perl code. This also means that if you want real +whitespace or C<#> characters in the pattern that you'll have to either +escape them or encode them using octal or hex escapes. Taken together, +these features go a long way towards making Perl's regular expressions +more readable. See the C comment deletion code in L<perlop>. =head2 Regular Expressions @@ -63,7 +83,7 @@ on the pattern match operator. (Older programs did this by setting C<$*>, but this practice is deprecated in Perl 5.) To facilitate multi-line substitutions, the "." character never matches a -newline unless you use the C</s> modifier, which tells Perl to pretend +newline unless you use the C</s> modifier, which in effect tells Perl to pretend the string is a single line--even if it isn't. The C</s> modifier also overrides the setting of C<$*>, in case you have some (badly behaved) older code that sets it in another module. |