use strict;
use warnings;
use diagnostics;

use Data::Dumper;

sub array_differenz ($$);

main();
exit;

sub main {
     my @a1 = qw/1 2 2 3 3 3 4 4 4 4/;
     my @a2 = qw/1 2 3 4/;
     my @a  = array_differenz(\@a1, \@a2);
     print "Ergebnis a:\n", Dumper \@a;

     my @b1 = qw/eins eins zwei/;
     my @b2 = qw/eins zwei/;
     my @b  = array_differenz(\@b1, \@b2);
     print "Ergebnis b:\n", Dumper \@b;
}

sub array_differenz ($$) {
     my $a1 = shift; # Array-Referenz
     my $a2 = shift; # Array-Referenz

     my @a1m2 = @$a1; # Array 1 minus Array 2;

     for my $element (@$a2) {
         for my $index (0..$#a1m2) {
             if ($element eq $a1m2[$index]) {
                 splice @a1m2, $index, 1;
                 last;
             }
         }
     }
 
     my @a2m1 = @$a2; # Array 2 minus Array 1;

     for my $element (@$a1) {
         for my $index (0..$#a2m1) {
             if ($element eq $a2m1[$index]) {
                 splice @a2m1, $index, 1;
                 last;
             }
         }
     }

     print "Array 1:\n", Dumper $a1;
     print "Array 2:\n", Dumper $a2;
     print "Array 1 minus Array 2:\n", Dumper \@a1m2;
     print "Array 2 minus Array 1:\n", Dumper \@a2m1;

     return (@a1m2, @a2m1);
}