If you are using Netscape, you can use HTTP::Cookies to have your LWP::UserAgent client read and write from your actual Netscape cookie files without needing to cut and paste the cookie string into your code:

#!/usr/bin/perl -w

use strict;
use HTTP::Cookies;
use LWP::UserAgent;

#Set path to your Netscape Cookie files
my $cookie_jar = HTTP::Cookies::Netscape->new(
  File     => "$ENV{HOME}/.netscape/cookies",
  AutoSave => 1,
);

#Create a User Agent, and tell it to store cookies
my $ua = LWP::UserAgent->new;
$ua->cookie_jar($cookie_jar);
#...
[download]

If you aren't using Netscape, then you will have to explicitly set the cookies in the $cookie_jar object, which you can do using the HTTP::Cookies::set_cookie() method.