$main = 'http://cgi3.ebay.com/aw-cgi/eBayISAPI.dll'; 
$ru = "http://encode_this/";
use URI;
my $uri = URI->new($main);
$uri->query_form(
  qw(MfcISAPICommand SignInWelcome userid userid pass pass keepMeSignInOption 1),
  ru => $ru
 );
print $uri->as_string;