diff options
Diffstat (limited to 'pod/perlre.pod')
| -rw-r--r-- | pod/perlre.pod | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/pod/perlre.pod b/pod/perlre.pod index c2b968062b..7df564738e 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -246,7 +246,9 @@ X<word> X<whitespace> so you may end up with malformed pieces of UTF-8. Unsupported in lookbehind. \1 Backreference to a specific group. - '1' may actually be any positive integer. + '1' may actually be any positive integer. + \R1 Relative backreference to a preceding closed group. + '1' may actually be any positive integer. \k<name> Named backreference \N{name} Named unicode character, or unicode escape \x12 Hexadecimal escape sequence @@ -469,7 +471,15 @@ ambiguity by interpreting \10 as a backreference only if at least 10 left parentheses have opened before it. Likewise \11 is a backreference only if at least 11 left parentheses have opened before it. And so on. \1 through \9 are always interpreted as -backreferences. +backreferences. + +X<relative backreference> +In Perl 5.10 it is possible to relatively address a capture buffer by +using the C<\RNNN> notation, where C<NNN> is negative offset to a +preceding completed capture buffer. Thus C<\R1> refers to the last +buffer closed, C<\R2> refers to the buffer before that, and so on. Note +especially that C</(foo)(\R1)/> refers to the capture buffer containing +C<foo>, not to the buffer containing C<\R1>. Additionally, as of Perl 5.10 you may use named capture buffers and named backreferences. The notation is C<< (?<name>...) >> and C<< \k<name> >> @@ -884,6 +894,9 @@ C<(?R)>. If PARNO is preceded by a plus or minus sign then it is assumed to be relative, with negative numbers indicating preceding capture buffers and positive ones following. Thus C<(?-1)> refers to the most recently declared buffer, and C<(?+1)> indicates the next buffer to be declared. +Note that the counting for relative recursion differs from that of +relative backreferences, in that with recursion unclosed buffers B<are> +included. The following pattern matches a function foo() which may contain balanced parentheses as the argument. |