#!/usr/bin/perl

use warnings;
use strict;

# my @a = (1, 2, 3, 4);
# my @b = (1, 3, 2, 5, 6);

my @a = ( 1, 2, 3, 4, 5, 6, 7, 8 );
my @b = ( 12, 13, 1, 2, 3, 4, 22 );

my %h = ();
my $i;

foreach $i (@b) {
    $h{$i} = 0;
}

foreach $i (@a) {
    if (exists($h{$i})) {
        $h{$i}++;
    } 
}

my @b2 = ();
foreach $i (@b) {
    if ($h{$i} == 0) {
        push(@b2, $i);
    }
}
foreach $i (@b2) {
    print "$i\n";
}