Tunnelbroker.net ipv4 updater / ipv6 configurator

#!/usr/bin/perl -w
#
# Perl script for tunnelbroker.net (hurricane electric)
# to update client ipv4 address of your ipv6 tunnel
# and configure ipv6 interface using linux-route2
#
# Developed by Roberto Tacconelli 28 Jan 2012 (01/28/2012)
# http://www.st4ck.com
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#

use WWW::Mechanize;

# Config
$username = "YOUR_USERNAME";
$password = "a123456789abcdef1234567890abcdef"; #md5 of your password
$tid = 12345; #your tunnel id from http://tunnelbroker.net/tunnel_detail.php?tid=YOUR_ID
$cipv6 = "2001:470:12:34::2/64"; #client ipv6 address
$sipv4 = "216.66.123.45"; #server ipv4 address
########

my $mech = WWW::Mechanize->new();

print "Retrieving external ip...\n";
$mech->get( "http://www.whatismyip.org" );
$ip = $mech->content;
print "Ok.\n";

print "\nConfiguring new ip: ".$ip." ...\n";

$url = "http://www.tunnelbroker.net";
$mech->get( $url );

$mech->submit_form(
        form_number => 0,
        fields      => {
            f_user    => $username,
            clearpass => '',
            f_pass    => $password,
        redir     => '',
        }
    );

$mech->post( "http://www.tunnelbroker.net/tunnel_detail.php?ajax=true&tid=".$tid, ["ipv4z" => $ip]);

print "Ok.\n";

print "\nSetting up network interface...\n";

`sudo modprobe ipv6`;
`sudo ip tunnel del he-ipv6`;
`sudo ip tunnel add he-ipv6 mode sit remote $sipv4 local $ip ttl 255`;
`sudo ip link set he-ipv6 up`;
`sudo ip addr add $cipv6 dev he-ipv6`;
`sudo ip route add ::/0 dev he-ipv6`;

print "Ok.\n";

print "\nSetting up dns...\n";
`cp /etc/resolv.conf /tmp/resolv.conf`;
`echo "nameserver 2620:0:ccc::2" >> /tmp/resolv.conf`;
`sudo cp /tmp/resolv.conf /etc/resolv.conf`;
print "Ok.\n";