List::Compare may well be what you are looking for - reinventing wheels and all that.

use warnings;
use strict;
use Data::Dump::Streamer;
use List::Compare;

my @A = ('1', '2', '4', '8');
my @B = ('1', '3', '6', '8');

my $lc = List::Compare->new (\@A, \@B);
my @intersect = $lc->get_intersection;

my @AOnly = $lc->get_Lonly;
my @BOnly = $lc->get_Ronly;

print "Intersection: @intersect\n";
print "A only: @AOnly\n";
print "B only: @BOnly\n";
[download]

Prints:

Intersection: 1 8
A only: 2 4
B only: 3 6
[download]