The following script demonstrates how to determine if there are duplicate elements in an array.

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

my @fruits = qw(orange apple orange grape pineapple banana);
my %seen;
foreach my $fruit (@fruits) {
  if ($seen{$fruit}++) {
    print "$fruit has already been seen \n";
  }
}

Running this script should return the following.

orange has already been seen
orange has already been seen