#!/usr/bin/perl
use strict;
use Digest::MD5;

my $file = shift;
my ($input, $check);

open($input, $file) or die "Could not open $file: $!";
open($check, $file) or die "Could not open $file: $!";

my %hash;

while (!eof($input)) {
    my $location = tell($input);
    my $line = readline($input);
    chomp $line;
    my $digest = Digest::MD5::md5($line);
#    $digest = length($line);
    if (defined(my $ll = $hash{$digest})) {
        my $d = 0;
        for my $l (@$ll) {
            seek($check, $l, 0);
            my $checkl = readline($check);
            chomp $checkl;
            if ($checkl eq $line) {
                print "DUP $line\n";
                $d = 1;
                last;
            }
        }
        if ($d == 0) {
            push(@{$hash{$digest}}, $location);
        }
    } else {
        push(@{$hash{$digest}}, $location);
    }
}