This is all explained very clearly in lwpcook. Here's the example it gives:

use HTTP::Request::Common qw(POST);
use LWP::UserAgent;
$ua = new LWP::UserAgent;
my $req = POST 'http://www.perl.com/cgi-bin/BugGlimpse',
                [ search => 'www', errors => 0 ];
print $ua->request($req)->as_string;
[download]

--
<http://www.dave.org.uk>

"Perl makes the fun jobs fun
and the boring jobs bearable" - me