Perl: Need an LWP & HTTP::Request POST code that actually works

Question

I have been scratching my head trying to get LWP and HTTP::Request to actually pass a POST parameter to a web server. The web server can see the fact that the request was a POST transaction, but it is not picking up the passed parameters. I have been searching all day on this and have tried different things and I have yet to find something that works. (The web server is working, I am able to manually send post transactions and when running the whole script, I am getting '200' status but I am not seeing any posted elements. Any help would be appreciated. Tnx.

my $ua2 = LWP::UserAgent->new;
$ua2->agent("Mozilla/5.0 (compatible; MSIE 6.0; Windows 98)");
my $req2 = HTTP::Request->new(POST => "$url", [ frm-advSearch => 'frmadvSearch' ]);
$req2->content_type('text/html');
my $res2 = $ua2->request($req2);
$http_stat = substr($res2->status_line,0,3);

Answer 1

my $res = $ua->post($url,
   Content => [
      'frm-advSearch' => 'frmadvSearch',
   ],
);

which is short for

use HTTP::Request::Common qw( POST );

my $req = POST($url,
   Content => [
      'frm-advSearch' => 'frmadvSearch',
   ],
);

my $res = $ua->request($req);

Answer 2

Here's a Mojo::UserAgent example, which I find easier to debug:

use Mojo::UserAgent;
my $ua = Mojo::UserAgent->new;
$ua->transactor->name( 'Mozilla/5.0 (compatible; MSIE 6.0; Windows 98)' );

my $url = 'http://www.example.com/form/';
my $tx = $ua->post( $url, form => { 'frm-advSearch' => 'frmadvSearch' } );
say $tx->req->to_string;

The transaction in $tx knows about the request so I can look at that:

POST /form/ HTTP/1.1
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (compatible; MSIE 6.0; Windows 98)
Accept-Encoding: gzip
Host: www.example.com
Content-Length: 26

frm-advSearch=frmadvSearch