#!/usr/bin/perl -w

use strict;

# Set up the arrays
my @array1 = qw(a b c d);
my @array2 = qw(b a e f);

# Create the hash, based on array1
my %hash;
foreach (@array1) {$hash{$_} = 1;}

# Loop through array2 looking for matches
foreach (@array2) {
    if ($hash{$_}) {print $_, "\n"}
}