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

my @array1=('a','2','3','2');
my @array2=('1','2','3','2');

my %in_array2 = map { $_ => 1 } @array2;

my @array3 = grep { $in_array2{$_} } @array1;

print "common @array3\n";

my %seen;
my @unique = grep{!$seen{$_}++} @array3;

print "unique @unique\n";