Perl Pocket Reference, 4th Edition

Chapter 23. Search and Replace Functions

[ expr =~ ] [ m ] /pattern/ [ g [ c ] ] [ i ] [ m ] [ o ] [ s ] [ x ]

Searches expr (default $_) for a pattern.

For =~, its negation !~ may be used, which is true when =~ would return false, and vice versa.

After a successful match, the following special variables are set:

$&	The string that matched.
$`	The string preceding what was matched.
$'	The string following what was matched.
$1	The first parenthesized subexpression that matched, $2 the second, and so on.
$+	The last subexpression that matched.
@-	The start offsets of the match and submatches.
@+	The corresponding end offsets.

If used in list context, a list is returned consisting of the subexpressions matched by the parentheses in pattern, i.e., ($1,$2,$3, . . . ).

Optional modifiers are:

c	(with g) prepares for continuation.
g	matches as many times as possible.
i	searches in a case-insensitive manner.
o	interpolates variables only once.
m	treats the string as multiple lines. ^ and $ will match at embedded newline characters.
s	treats the string as a single line. . will match embedded newline characters.
x	allows for whitespace and comments.

If pattern is empty, the most recent pattern from a previous successful m// or s/// is used.

With g, the match in scalar context can be used as an iterator. The iterator is reset upon failure, unless c is also supplied.

See generic Chapter 6.

?pattern?

This is just like the /pattern/ search, except that it matches only once between calls to the reset operator.

[ $var =~ ] s /pattern ...