Perl 5.10 Named Capture Bug?

delfarms has asked for the wisdom of the Perl Monks concerning the following question:

Please see Python code, then the Perl equivalent:

import re
r = re.compile(r'(?P<A> a (?P<B> b))', re.X)
m = r.search('ab')
for k in m.groupdict():     
    print k, '=>', m.group(k)    # 'A => ab'             
                                 # 'B => b'
print m.group('A')               # 'ab'
print m.group('B')               # 'b'
[download]

Perl equivalent:

'ab' =~ /(?<A> a (?<B> b))/x;
print "$_ => $+{$_}\n" for (keys(%+));    # 'A => ab'
                                          # ... nothing, thats it
print "$+{'A'}\n";                        # 'ab'
print "$+{'B'}\n";                        # 'b'
[download]

Perl doesn't enumerate all the keys if a named capture is nested within another. But it it clearly holds the correct value 'b' with the correct key 'B' in the hash. Is this a "feature" or a bug? ;)

Comment on Perl 5.10 Named Capture Bug? Select or Download Code

Replies are listed 'Best First'.
Re: Perl 5.10 Named Capture Bug? by SankoR (Prior) on Jul 08, 2008 at 21:10 UTC
I'll trust moritz that it's a feature, but it's one that has been fixed (...or removed as features don't require a fix ;) in bleadperl.	[reply]
Re^2: Perl 5.10 Named Capture Bug? by moritz (Cardinal) on Jul 08, 2008 at 22:24 UTC
Please don't trust anything I wrote just because it was me who wrote it. Same for other saints. We're human, we err, and sometimes we just misread questions ;-) (I assume that was just a polite and humorous way to tell me that I'm wrong, but if not I'd like to correct that view)	[reply]
Re: Perl 5.10 Named Capture Bug? by moritz (Cardinal) on Jul 08, 2008 at 20:42 UTC
~~This is a feature, because it's analog to the case of positional captures.~~ ~~Perl 6 introduces properly nested match objects.~~ Sorry, I misread the question. I thought you were expecting nested hashes in `%+`. And no, It's a bug, not a feature. Sorry for the noise.	[reply] [d/l]
Re^2: Perl 5.10 Named Capture Bug? by delfarms (Novice) on Jul 08, 2008 at 22:45 UTC
No worries moritz. Thank you both for the fast and helpful replies. Cheers!	[reply]
Re: Perl 5.10 Named Capture Bug? by maletin (Sexton) on Jul 09, 2008 at 11:57 UTC
I think, you want to use %- and not %+. see also "perldoc perlre" and "perldoc perlvar".	[reply]