I think in your second example, your if statement is testing the wrong variable. Compare with this code:

         my $foo = [
                 { foo => { bar => 'baz' } },
         ];

         foreach my $foo_entry (@$foo)
         {
                 foreach (keys %$foo_entry)
                 {
                         if (defined($foo_entry->{$_}->{foo})
                          && defined($foo_entry->{$_}->{foo}->{bar}))
                         {
                                 return $foo_entry->{$_}->{foo}->{bar}
+;
                         }
                 }

                 return;
         }
[download]

In the inner loop, $_ is a key of %$foo_entry. I'm not sure why your code passes strict, since $foo should contain an array ref and not a hash ref; I'd expect the if statement to bomb with "not a hashref".

I'm also confused about your question: Do you know the answer, and you're testing us, or have you still not figured out what's wrong?

Thanks :)

Update: On FreeBSD, perl 5.6.0, I get:

% perl hoh.pl
Out of memory during "large" request for 1073745920 bytes at hoh.pl line 15.

So, Yes it tries to gobble up lots of memory :) But luckily it fails all at once instead of eating swap and bombing the entire system.

Alan