another 'POST from perl' question

[JD]

Hi,
I've searched for several weeks, and I've found code that should allow
me to post from my perl script. I continue to fail, though.
Admittedly, I am not good with OOP (other than VB). I'm trying to post
so as to process credit card info, and authorize.net states that I must
POST with a query string (?), but don't use GET. In short, I've tried:
use CGI; use LWP::UserAgent; use HTTP::Request;
use HTTP::Status; $cgi = new CGI;
my $ua = LWP::UserAgent->new;
my $submit_str = "x_login=$acct_id&x_tran_key=$tran_key";
my $request = new HTTP::Request 'POST', $transaction_server;
$request->content_type('application/x-www-form-urlencoded');
$request->content($submit_str);
my $response = $ua->request($request);
$resp = $response->content;
if ($response->is_success) { print "Success"; }
else { print "Fail"; }

and I've tried a combination of variations:
my $response = $ua->request(POST $transaction_server,
['x_login' => $acct_id, 'x_tran_key' => $tran_key],);

including passing my data as a query_string, but I just can't make it to
is_success. I also can't decipher the hash that LWP appears to return.

I've looked at cpan, perl.com, and my cookbook, but to no avail. Tech
support doesn't support scripts, so they're little help.

Any suggestions or help? I apologize for my ignorance.
Thank you,
-jd