diff options
Diffstat (limited to 'pod/perlre.pod')
| -rw-r--r-- | pod/perlre.pod | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/pod/perlre.pod b/pod/perlre.pod index 7133a02c96..d886d094a7 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -586,6 +586,15 @@ already paid the price. As of 5.005, C<$&> is not so costly as the other two. X<$&> X<$`> X<$'> +As a workaround for this problem, Perl 5.10 introduces C<${^PREMATCH}>, +C<${^MATCH}> and C<${^POSTMATCH}>, which are equivalent to C<$`>, C<$&> +and C<$'>, B<except> that they are only guaranteed to be defined after a +successful match that was executed with the C</k> (keep-copy) modifier. +The use of these variables incurs no global performance penalty, unlike +their punctuation char equivalents, however at the trade-off that you +have to tell perl when you want to use them. +X</k> X<k modifier> + 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 @@ -639,7 +648,7 @@ 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 C<(?imsx-imsx)> +=item C<(?kimsx-imsx)> X<(?)> One or more embedded pattern-match modifiers, to be turned on (or @@ -667,6 +676,11 @@ will match a repeated (I<including the case>!) word C<blah> in any case, assuming C<x> modifier, and no C<i> modifier outside this group. +Note that the C<k> modifier is special in that it can only be enabled, +not disabled, and that its presence anywhere in a pattern has a global +effect. Thus C<(?-k)> and C<(?-k:...)> are meaningless and will warn +when executed under C<use warnings>. + =item C<(?:pattern)> X<(?:)> |