use HTTP::Request::Common qw(GET POST);
use HTTP::Cookies;
use LWP::UserAgent;
...
my $ua = new LWP::UserAgent();
my $cookies = new HTTP::Cookies(file => 'cookies.dat',
                                autosave => 1);
$ua->cookie_jar($cookies);

# We now have a persistent cookie jar associated with the
# user agent.

my $req = GET "$url";

# if the response included a cookie, it'll be saved in the
# jar, and resent along with subsequent GETs or POSTs to
# the same domain that issued the cookie.