#!/usr/bin/perl

use strict;
use warnings;

my $num_duplicates = 0;
my $last           = '';
while (<DATA>) {
    chomp;
    if ( $_ eq $last ) {
        $num_duplicates++;
    }
    else {
        print "$_\n";
        $last = $_;
    }
}

print "There where $num_duplicates duplicates.\n";

__DATA__
apple
banana
banana
cherry
date
date
date
elderberry

##</code><code>##

apple
banana
cherry
date
elderberry
There where 3 duplicates.