use strict;
use warnings;
use Data::Dumper;

my @a = (43,43,44);
my @b = (43,43);
my @c= difference(\@a, \@b);
print Dumper \@c;

my @p = ( 1,1,1,1,1,2,2,2,3,3,4,5,6);
my @q = ( 1,2,3,4,5,6 );
my @r= difference(\@p, \@q);
print Dumper \@r;

sub difference {
	my ($a, $b)= @_;
	my %d;
	++$d{$_} foreach @$a;
	--$d{$_} foreach @$b;
	return map { ($_) x abs $d{$_} } keys %d;
}