Hashes are good for determining uniqueness of things. The grep tests every value in @array2 and populates @common with each value that returns true.

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump;

my @array1 = (1,2,3,4);
my @array2 = (4,5,6,7);

my %hash;
@hash{@array1} = undef; #Hash Slice populates keys of hash using value
+s from array

my @common = grep { exists $hash{$_} } @array2;

dd @common; #4
[download]