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

my @list_of_items = qw(a b c a d b b z f);

my %seen;

foreach my $item (@list_of_items) {
    if($seen{$item}++) {
        # do what is appropriate for items that have already been seen
        print "saw an $item again\n";
    } else {
        # do what is appropriate for items that have not already been seen
        print "saw an $item\n";
    }
}

foreach my $item (sort keys %seen) {
    print "$item is in \@list_of_items $seen{$item} " . (($seen{$item} > 1)?"times\n":"time\n");
}