X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlretut.pod;h=6e06f192914b95af82e9cb85856ac46daf6a111f;hb=376270a4000241675d2fdcb89a2b30a7bb0e3695;hp=4ea9ecc497a48d3b38c3c826050f09a061bc5431;hpb=48e3bbddf569369fe6921f305df6ab7290c91152;p=p5sagit%2Fp5-mst-13.2.git
diff --git a/pod/perlretut.pod b/pod/perlretut.pod
index 4ea9ecc..6e06f19 100644
--- a/pod/perlretut.pod
+++ b/pod/perlretut.pod
@@ -689,10 +689,11 @@ inside goes into the special variables C<$1>, C<$2>, etc. They can be
used just as ordinary variables:
# extract hours, minutes, seconds
- $time =~ /(\d\d):(\d\d):(\d\d)/; # match hh:mm:ss format
- $hours = $1;
- $minutes = $2;
- $seconds = $3;
+ if ($time =~ /(\d\d):(\d\d):(\d\d)/) { # match hh:mm:ss format
+ $hours = $1;
+ $minutes = $2;
+ $seconds = $3;
+ }
Now, we know that in scalar context,
S > returns a true or false
@@ -1403,7 +1404,8 @@ off. C<\G> allows us to easily do context-sensitive matching:
The combination of C/g> and C<\G> allows us to process the string a
bit at a time and use arbitrary Perl logic to decide what to do next.
-Currently, the C<\G> anchor only works at the beginning of a pattern.
+Currently, the C<\G> anchor is only fully supported when used to anchor
+to the start of the pattern.
C<\G> is also invaluable in processing fixed length records with
regexps. Suppose we have a snippet of coding region DNA, encoded as
@@ -1706,7 +1708,7 @@ it matches I byte 0-255. So
The last regexp matches, but is dangerous because the string
I position is no longer synchronized to the string I
position. This generates the warning 'Malformed UTF-8
-character'. C<\C> is best used for matching the binary data in strings
+character'. The C<\C> is best used for matching the binary data in strings
with binary data intermixed with Unicode characters.
Let us now discuss the rest of the character classes. Just as with
@@ -2003,6 +2005,10 @@ They evaluate true if the regexps do I match:
$x =~ /foo(?!baz)/; # matches, 'baz' doesn't follow 'foo'
$x =~ /(? is unsupported in lookbehind, because the already
+treacherous definition of C<\C> would become even more so
+when going backwards.
+
=head2 Using independent subexpressions to prevent backtracking
The last few extended patterns in this tutorial are experimental as of