diff options
| -rw-r--r-- | pod/perldelta.pod | 28 | ||||
| -rw-r--r-- | pod/perlop.pod | 7 | ||||
| -rw-r--r-- | pod/perlre.pod | 7 |
3 files changed, 28 insertions, 14 deletions
diff --git a/pod/perldelta.pod b/pod/perldelta.pod index 4aa05edc82..fdd4dde722 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -350,15 +350,25 @@ of course, or if you want a seed other than the default. Functions documented in the Camel to default to $_ now in fact do, and all those that do are so documented in L<perlfunc>. -=item C<m//g> does not trigger a pos() reset on failure - -The C<m//g> match iteration construct used to reset the iteration -when it failed to match (so that the next C<m//g> match would start at -the beginning of the string). You now have to explicitly do a -C<pos $str = 0;> to reset the "last match" position, or modify the -string in some way. This change makes it practical to chain C<m//g> -matches together in conjunction with ordinary matches using the C<\G> -zero-width assertion. See L<perlop> and L<perlre>. +=item C<m//g> does not reset search position on failure + +The C<m//g> match iteration construct used to reset its target string's +search position (which is visible through the C<pos> operator) when a +match failed; as a result, the next C<m//g> match would start at the +beginning of the string). With Perl 5.004, the search position must be +reset explicitly, as with C<pos $str = 0;>, or by modifying the target +string. This change in Perl makes it possible to chain matches together +in conjunction with the C<\G> zero-width assertion. See L<perlop> and +L<perlre>. + +Here is an illustration of what it takes to get the old behavior: + + for ( qw(this and that are not what you think you got) ) { + while ( /(\w*t\w*)/g ) { print "t word is: $1\n" } + pos = 0; # REQUIRED FOR 5.004 + while ( /(\w*a\w*)/g ) { print "a word is: $1\n" } + print "\n"; + } =item C<m//x> ignores whitespace before ?*+{} diff --git a/pod/perlop.pod b/pod/perlop.pod index 45dafaa187..3bd4f21511 100644 --- a/pod/perlop.pod +++ b/pod/perlop.pod @@ -701,7 +701,10 @@ matches. (In other words, it remembers where it left off last time and restarts the search at that point. You can actually find the current match position of a string or set it using the pos() function--see L<perlfunc/pos>.) Note that you can use this feature to stack C<m//g> -matches or intermix C<m//g> matches with C<m/\G.../>. +matches or intermix C<m//g> matches with C<m/\G.../g>. Note that +the C<\G> zero-width assertion is not supported without the C</g> +modifier; currently, without C</g>, C<\G> behaves just like C<\A>, but +that's accidental and may change in the future. If you modify the string in any way, the match position is reset to the beginning. Examples: @@ -724,7 +727,7 @@ beginning. Examples: print "1: '"; print $1 while /(o)/g; print "', pos=", pos, "\n"; print "2: '"; - print $1 if /\G(q)/; print "', pos=", pos, "\n"; + print $1 if /\G(q)/g; print "', pos=", pos, "\n"; print "3: '"; print $1 while /(p)/g; print "', pos=", pos, "\n"; } diff --git a/pod/perlre.pod b/pod/perlre.pod index f881a3bcc7..ed9c5334b8 100644 --- a/pod/perlre.pod +++ b/pod/perlre.pod @@ -163,7 +163,7 @@ Perl defines the following zero-width assertions: \B Match a non-(word boundary) \A Match at only beginning of string \Z Match at only end of string (or before newline at the end) - \G Match only where previous m//g left off + \G Match only where previous m//g left off (works only with /g) A word boundary (C<\b>) is defined as a spot between two characters that has a C<\w> on one side of it and a C<\W> on the other side of it (in @@ -173,9 +173,10 @@ represents backspace rather than a word boundary.) The C<\A> and C<\Z> are just like "^" and "$" except that they won't match multiple times when the C</m> modifier is used, while "^" and "$" will match at every internal line boundary. To match the actual end of the string, not ignoring newline, -you can use C<\Z(?!\n)>. The C<\G> assertion can be used to mix global -matches (using C<m//g>) and non-global ones, as described in +you can use C<\Z(?!\n)>. The C<\G> assertion can be used to chain global +matches (using C<m//g>), as described in L<perlop/"Regexp Quote-Like Operators">. + It is also useful when writing C<lex>-like scanners, when you have several regexps which you want to match against consequent substrings of your string, see the previous reference. |