diff options
Diffstat (limited to 'pod/perlre.pod')
| -rw-r--r-- | pod/perlre.pod | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/pod/perlre.pod b/pod/perlre.pod index 4e683a37f4..bce72914fb 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -1094,6 +1094,48 @@ Any number of C<(?COMMIT)> assertions may be used in a pattern. See also C<< (?>pattern) >> and possessive quantifiers for other ways to control backtracking. +=item C<(?CUT)> +X<(?CUT)> + +This zero-width pattern is similar to C<(?COMMIT)>, except that on +failure it also signifies that whatever text that was matched leading +up to the C<(?CUT)> pattern cannot match, I<even from another +starting point>. + +Compare the following to the examples in C<(?COMMIT)>, note the string +is twice as long: + + 'aaabaaab'=~/a+b?(?CUT)(?{print "$&\n"; $count++})(?FAIL)/; + print "Count=$count\n"; + +outputs + + aaab + aaab + Count=2 + +Once the 'aaab' at the start of the string has matched and the C<(?CUT)> +executed the next startpoint will be where the cursor was when the +C<(?CUT)> was executed. + +=item C<(?ERROR)> +X<(?ERROR)> + +This zero-width pattern is similar to C<(?CUT)> except that it causes +the match to fail outright. No attempts to match will occur again. + + 'aaabaaab'=~/a+b?(?ERROR)(?{print "$&\n"; $count++})(?FAIL)/; + print "Count=$count\n"; + +outputs + + aaab + Count=1 + +In other words, once the C<(?ERROR)> has been entered and then pattern +does not match then the regex engine will not try any further matching at +all on the rest of the string. + =item C<(?(condition)yes-pattern|no-pattern)> X<(?()> |