comp (\% hash1, \%hash2);

sub comp {
  my $hash1 = shift;
  my $hash2 = shift;

  if( keys %{$hash1} != keys %{$hash2} ) {
    print "Hash1 has ", scalar(keys %{$hash1}),
          " units but hash2 has ", scalar(keys %{$hash2}), "\n";
  }

  for my $key_hash1 (sort {lc($a) cmp lc($b) } keys %{$hash1} ) {
    if( ! exists $hash2->{$key_hash1} ) {
      print "Hash1 contains unit '$key_hash1' but hash2 has no such unit\n";
      next;
    }
    if( $hash1->{$key_hash1} ne $hash2->{$key_hash1} ) {
      print "Both hashes have '$key_hash1' as a unit ",
            "but hash1's value is '$hash1->{$key_hash1}' ",
            "and hash2's value is '$hash2->{$key_hash1}'\n";
    }
  }
}