#! /usr/bin/perl -w
use strict;
my @a = (1,2,3,4,5);
my @b = (2,4,6,8);
my %c;
@c{@a} = undef;
my @bb = grep { ! exists $c{$_} } @b;     
my %d;
@d{@b} = undef;
my @aa = grep { ! exists $d{$_} } @a;
print "@aa\n";
print "@bb\n";

##</code><code>##

1 3 5
6 8