#!/opt/perl5/bin/perl -w

use strict;

my %lines; 
my @dupes;

while($_ =<> and $_ ne "quit\n"){
	$lines{$_}++;        
	if($lines{$_} == 2){ 
 		push @dupes, $_;
 	}
}
if(@dupes){
 	print "Here are your duplicate lines\n\n";
 	foreach(@dupes){
 		print $_;
 	}
} else {
  	print "\nNo Duplicates Found!\n";
}


##</code><code>##

Value of <HANDLE> construct can be "0"; test with defined() at day1_test.1.pl line 8.