use RPC::XML;

    $req = RPC::XML::request->new('fetch_prime_factors',
                                  RPC::XML::int->new(985120528));
    ...
    $resp = RPC::XML::Parser->new()->parse(STREAM);
    if (ref($resp))
    {
        return $resp->value->value;
    }
    else
    {
        die $resp;
    }