in reply to how can i return the common keys from a hash

This is a typical intersection problem. Yes, a FAQ. Go read perlfaq4. You basically create some arrays with the hash keys and perform the intersection over them.

Update: Hmm, seems I misread "values". Well, you can perform the intersection of the values as it's explained in the FAQ. For obtaining the corresponding keys, you can reverse the hash:

my %c = ( a=>1, b=>2, c=>3 );
my %rev_c = reverse %c;
use Data::Dumper;print Dumper \%rev_c;
__END__
$VAR1 = {
          '1' => 'a',
          '3' => 'c',
          '2' => 'b'
        };

[download]

Of course, you're going to have problems if there's more than one key with the same value, since the action of reversing the hash will eliminate all of those keys but one.

--
David Serrano

In Section Seekers of Perl Wisdom