diff options
Diffstat (limited to 'pod/perlre.pod')
| -rw-r--r-- | pod/perlre.pod | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/pod/perlre.pod b/pod/perlre.pod index 704878780b..5af167b820 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -454,7 +454,8 @@ a backreference only if at least 11 left parentheses have opened before it. And so on. C<\1> through C<\9> are always interpreted as backreferences. You can minimize the ambiguity by always using C<\g> if you mean capturing groups; and always using 3 digits for octal constants, with the first always "0" (which -works if there are 63 (= \077) or fewer capture groups). +works if there are 63 (= \077) or fewer capture groups). There are several +examples below that illustrate these perils. The C<\I<digit>> notation also works in certain circumstances outside the pattern. See L</Warning on \1 Instead of $1> below for details.) @@ -478,6 +479,20 @@ Examples: $seconds = $3; } + /(.)(.)(.)(.)(.)(.)(.)(.)(.)\g10/ # \g10 is a backreference + /(.)(.)(.)(.)(.)(.)(.)(.)(.)\10/ # \10 is octal + /((.)(.)(.)(.)(.)(.)(.)(.)(.))\10/ # \10 is a backreference + /((.)(.)(.)(.)(.)(.)(.)(.)(.))\010/ # \010 is octal + + $a = '(.)\1'; # Creates problems when concatenated. + $b = '(.)\g{1}'; # Avoids the problems. + "aa" =~ /${a}/; # True + "aa" =~ /${b}/; # True + "aa0" =~ /${a}0/; # False! + "aa0" =~ /${b}0/; # True + "aa\x8" =~ /${a}0/; # True! + "aa\x8" =~ /${b}0/; # False + Several special variables also refer back to portions of the previous match. C<$+> returns whatever the last bracket match matched. C<$&> returns the entire matched string. (At one point C<$0> did |