#!/usr/bin/perl -w

use strict;

my @array1 = qw[a b c d e];
my @array2 = qw[t e s t d a t a];

my @sort1 = sort @array1;
my @sort2 = sort @array2;

while (@sort1 && @sort2) {
  if ($sort1[0] eq $sort2[0]) {
    my $match = $sort1[0];
    while (@sort1 && $sort1[0] eq $match) { shift @sort1; }
    while (@sort2 && $sort2[0] eq $match) { shift @sort2; }
    print "$match is in both arrays\n";
  } elsif ($sort1[0] lt $sort2[0]) {
    shift @sort1;
  } else {
    shift @sort2;
  }
}