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;
    }

##</code><code>##

  for my $key_hash2 (sort {lc($a) cmp lc($b) } keys %{$hash2} ) {
    if( ! exists $hash1->{$key_hash2} ) {
      print "Hash1 contains unit '$key_hash2' but hash1 has no such unit\n";
    }
  }

##</code><code>##

    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";
    }

##</code><code>##

  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;
    }
    for my $key_hash1_tier2 (sort {lc($a) cmp lc($b) } keys %{$hash1->{$key_hash1}} ) {
      if( ! exists $hash2->{$key_hash1}{$key_hash1_tier2} ) {
        print "Hash1 $key_hash1 contains unit '$key_hash1_tier2' but hash2 has no such unit\n";
        next;
      }
      if( $hash1->{$key_hash1}{$key_hash1_tier2} ne $hash2->{$key_hash1}{$key_hash1_tier2} ) {
        print "Both hashes have '$key_hash1'-'$key_hash1_tier2' as a unit ",
              "but hash1's value is '$hash1->{$key_hash1}{$key_hash1_tier2}' ",
              "and hash2's value is '$hash2->{$key_hash1}{$key_hash1_tier2}'\n";
      }
    }
  }