Document trap with //o and closures

Subject: Re: Possible bug: /o overeager in closure constructor

Chip Salzenberg <chip@atlantic.net> wrote:
|
| According to Charles Bailey:
| > OK, so eval "" is the current workaround (but not eval '', if some of
| > the lexicals come from a block scope :-)).  Should this be documented?
| 
| IMO, it deserves an entry in perltrap.

How 'bout something like

=item * Regular Expression

Currently, if you use the /o qualifier on a regular expression within
an anonymous subroutine, I<all> closures generated from that anonymous
sub constructor will use the regular expression compiled the very
first time the constructor was called.  For instance, if you say

    sub build_match {
       my($left,$right) = @_;
       return sub { $_[0] =~ /$left stuff $right/o; };
    }

build_match will always return a sub which matches the contents of
C<$left> and <$right> from the first time it was called, not from
the current call.  This is probably a bug, and may change in future
versions of Perl.

It's a bit long, but I can't think of a more concise explanation
that's not confusing.

BTW, should we have a perlbugs.pod or somesuch as a home for things
like this, which aren't so much stable changes in the language as
problems we haven't been able to sort out yet?

p5p-msgid: 01IGCHWRNSEU00661G@hmivax.humgen.upenn.edu

1 files changed, 17 insertions, 0 deletions

diff --git a/pod/perltrap.pod b/pod/perltrap.pod
index 17c576df2f..c31d299284 100644
--- a/pod/perltrap.pod
+++ b/pod/perltrap.pod
@@ -1127,6 +1127,23 @@ found using the C<pos()> function--see L<perlfunc/pos>).
 You may always reset the iterator yourself as shown in the commented line
 to get the old behavior.
 
+=item * Regular Expression
+
+Currently, if you use the /o qualifier on a regular expression within
+an anonymous subroutine, I<all> closures generated from that anonymous
+sub constructor will use the regular expression compiled the very
+first time the constructor was called.  For instance, if you say
+
+    sub build_match {
+       my($left,$right) = @_;
+       return sub { $_[0] =~ /$left stuff $right/o; };
+    }
+
+build_match will always return a sub which matches the contents of
+C<$left> and <$right> from the first time it was called, not from
+the current call.  This is probably a bug, and may change in future
+versions of Perl.
+
 =back
 
 =head2 Subroutine, Signal, Sorting Traps