#!/usr/bin/perl
use strict;
use warnings;

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 "Result a:\n", Dumper \@a;

    print "-"x40, "\n";

    my @b1 = qw/one one two/;
    my @b2 = qw/one two/;
    my @b  = array_differenz(\@b1, \@b2);
    print "Result b:\n", Dumper \@b;

    print "-"x40, "\n";

    my @c1 = qw/one one two/;
    my @c2 = qw/one two three/;
    my @c  = array_differenz(\@c1, \@c2);
    print "Result c:\n", Dumper \@c;

} # sub main


sub array_differenz ($$) {
    my $a1   = shift; # array reference
    my $a2   = shift; # array reference

    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);

} # sub array_differenz