Reverse IP Perl Script [Perl]

#!/usr/bin/perl
#Reverse IP script.
#-----------------------------
#By Vulnerabiility
#Written by DNI
# Perl Version ( fast speed )
# Original Advisory :
# https://Vulnerabiility.googlecode.com/files/reverse-ip.pl

use LWP::UserAgent;
while (!$ARGV[0]) {
print q(
###############################################################
#                   Reverse IP Tools v.0.1                    #
###############################################################
#     usage : reverse-ip.pl [IP]                              #
#-------------------------------------------------------------#
#    [IP] : IP Address of site             (74.125.135.121)   #
###############################################################
#                   (c)oded by Vulnerabiility                 #
#                       Written by 3k0Nur                     #
#                  Greets : Surabaya Blackhat                 #
###############################################################
);exit;}
$a = 1;
$ua = new LWP::UserAgent(timeout => 15, agent => "Mozilla/5.0 (x11; u; linux i686; en-US; rv:1.8.0.7) Gecko/20060909 Firefox/1.5.0.7)" );
print " . . Scanning host on IP $ARGV[0] . . \n\n";
$req = $ua->get('http://whois.webhosting.info/' . $ARGV[0] . '?pi=1&ob=SLD&oo=ASC');
if (!($req->is_success)) {

die $req->status_line; }
else {
$output = $req->as_string;
until ($output =~ /(.*?)IP\sDetails\s-\sN\/A\./) {
$req = $ua->get('http://whois.webhosting.info/' . $ARGV[0] . '?pi=' . $a . '&ob=SLD&oo=ASC');
if (!($req->is_success)) { die $req->status_line; }
$output = $req->as_string;

while ($output =~ /<td><a\shref=\"http:\/\/whois.webhosting.info\/(.*?)\">/g){
my($crap,$yes)=split(/info\/(.*?)\.\"\>/,$&);
print "$yes\n";
}
sleep 5;
$a++;
}
print "Done!\n";
}