Thanks for your reply, although I'm still misisng it. I ran the program again, went down to the line that had the "Location:" header, and copied the redirection URI into my code, which is below:

#!/opt/gnu-irix/bin/perl

use strict;

use HTTP::Request::Common;
use LWP::UserAgent;

my $ua = new LWP::UserAgent;

#my $formurl = 'http://www.usps.com:80/cgi-bin/zip4/zip4inq2';
my $formurl = 
'http://148.129.65.3:80/fwauthredirect148.129.65.9id0003869786';
my $formdata = [
  'Firm' => '',
  'Urbanization' => '',
  'Delivery Address' => '100 Southland Vlg',
  'City' => '',
  'State' => '',
  'Zip Code' => '36079-3044',
  'Submit' => 'Process'
];

print $formurl, "\n";
my $resp = $ua->request(POST $formurl, $formdata);

if ($resp->is_success())
{
  print $resp->content();
}
else
{
  print "Problem\n\n", $resp->as_string();
}
[download]

Running the program generated a similar response:

HTTP/1.0 302 (Found) Not Allowed
Location: http://148.129.65.3:80/fwauthredirect148.129.65.9id000386993
+7
Content-Length: 120
Content-Type: text/html
Client-Date: Wed, 15 May 2002 15:57:42 GMT
Client-Peer: 56.0.78.101:80

Your request is being redirected to :<a href="http://148.129.65.3:80/f
+wauthredirect148.129.65.9id0003869937">here</a>.
[download]

It appears that I simply got redirected again. Please advise. Thanks.