Actually, the way you are doing it, you are comparing arrays. Therefore you may find useful this node:

comparing arrays

The best method there was MeowChow's at (MeowChow) Re2: (Efficiently) comparing arrays

To take advantage of hashes capabilities, though, I would rather use something like

#!/usr/bin/perl -w
use strict;

my %first = ( aa => 1, bb => 2, cc => 3, ee => 6);
my %second = ( bb=> 2, cc => 3, dd => 4 );

sub compare_one_hash_keys {
    my ($h1, $h2) = @_;
    return grep ( {not exists $h2->{$_} } keys %$h1)
}

sub compare_both_hash_keys {
    my ($h1, $h2) = @_;
    return grep ( {not exists $h2->{$_} } keys %$h1),
           grep ( {not exists $h1->{$_} } keys %$h2) ;
}

print  compare_one_hash_keys( \%first, \%second), "\n";
print  compare_one_hash_keys( \%second, \%first), "\n";
print  compare_both_hash_keys( \%first, \%second), "\n";

__END__
prints:
aaee
dd
aaeedd

[download]

The first sub returns an array of keys present in one hash and missing in the other one. The second one combines the differences in both hashes. I think you may use this method to implement what is closer to your needs.

 _  _ _  _  
(_|| | |(_|><
 _|

In reply to Re: Comparing all keys in a hash by gmax
in thread Comparing all keys in a hash by rinceWind

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.