Hi, you can also use something like:

$res = $ua->request(POST 'https://adwords.google.com/select/main',
             ['login.userid'       => 'test@test.com', 
              'login.password'     => 'testabc',
              'cmd'             => 'LoginValidation',
              'login'            => 'Login' ],
              Referer => $referer );
[download]

Also is good point for things like this, to set cookie jar:

my $cookie_jar = HTTP::Cookies->new;
my $ua = LWP::UserAgent->new;
$ua->cookie_jar($cookie_jar);
[download]

Hope that this will help you.
Regards
Li Tin O've Weedle
mad Tsort's philosopher