while (my $row= $csv->getline_hr($fh))
{
        $linecounter++;
        my $ip=$row->{'Source address'};
        my $url=$row->{'URL/Filename'};

        push @{ $ipURL{$ip} }, $url;

        if (!($linecounter % 50000))
        {
                print "Lines: $linecounter\n";
        }
}
        formatOutput(\%ipURL);
#       print Dumper \%ipURL;


##</code><code>##

perl test-urlListbyIP.pl
Lines: 50000
Lines: 100000
Lines: 150000
Lines: 200000
Lines: 250000
Lines: 300000
Lines: 350000
Lines: 400000
Lines: 450000
Lines: 500000
Lines: 550000
Lines: 600000
Lines: 650000
Lines: 700000
Lines: 750000
Lines: 800000
Lines: 850000
Formatting Output...
List End:1316
Execution Time: 44.18 s