I use cookies with WWW::Mechanize, but not only saving cookies for the session, saving cookies for later sessions as set by the site's "remember me on this computer"* checkbox.

my $browser = WWW::Mechanize->new(
    cookie_jar => {
        file     => "$ENV{HOME}/.cookies.txt",
        autosave => 1
    }
);
[download]

That script logged into the NY Times two years ago and has stayed logged in ever since.

* It should be "remember me on this computer with this browser" of course, but what the hell...