my @keys = keys (%$hash_ref);
foreach my $k (sort {lc $keys[$a] cmp lc $keys[$b]} 0..$#keys) {
        print "$keys[$k] => ";
        if (ref($hash_ref -> {$keys[$k]}) eq 'ARRAY') {
                print "(Untermenge wie folgt:)\n";
#               my @keys2 = keys %{$hash_ref -> {$keys[$k]}};
                my @keys2 = $hash_ref -> {$keys[$k]};
                foreach my $k2 (sort {lc $keys2[$a] cmp lc $keys2[$b]} 0..$#keys2) {
                        print "\t\t$keys2[$k2] => " . (defined $hash_ref -> {$keys2[$k2]} -> {$keys2[$k2]} ? $hash_ref -> {$keys2[$k2]} -> {$keys2[$k2]} : 'NOT DEFINED') . "\n";
                }
        }
        else {
                print (defined $hash_ref -> {$keys[$k]} ? $hash_ref -> {$keys[$k]} : 'NOT DEFINED');
        }
        print "\n";
}