I don't know pilgrim, but I tried your code and I don't see anything wrong with any of it. I created a bogus page: 
#!/usr/bin/perl -w
use strict;
use CGI qw/:standard/;
CGI::initialize_globals();
print header;
print start_html($ENV{'QUERY_STRING'});
if (!defined(param('j_username'))) {
  print start_form(-name=>'a_form', -method=>'GET', -action=>'login.cg
+i');
  print textfield(-name=>'j_username');
  print br,password_field(-name=>'j_password');
  print br,submit();
  print end_form;
} else {
 if ((defined(param('j_password'))) and (param('j_password') eq '1234'
+)) {
   print h1('YEAH!');
 } else {
   print h1('Bummer, wrong password!');
   }
}
print end_html;
1;

[download]
And ran your code and a debug and look at the response means that it got the data just fine: 
#!/usr/local/bin/perl -w

use strict;
use warnings;
use WWW::Mechanize;

my $url  = 'http://localhost/cgi-bin/login.cgi';
my $ua   = WWW::Mechanize->new();
my $user = 'foobie';
my $clearpass = '1999';
$ua->get($url);

#$ua->form_number('1');
#$ua->field('j_username',$user);
#$ua->field('j_password',$clearpass);
#$ua->submit();

$ua->set_fields("j_username" => $user, "j_password" => $clearpass);
$ua->submit();
if ($ua->success())
{ print "Yay!"; }
else
{ print "Login failed: " . $ua->response->status_line; }

[download]
I get: 
 # from perl -d node_298151.pl

  DB<7> p $ua->res->{'_content'}
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html
        PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
        "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US"><head><title>j
+_username=
foobie&amp;j_password=1999</title>
</head><body><h1>Bummer, wrong password!</h1></body></html>
  DB<8>

[download]
Which responds correctly because I issue a bad password (1999 instead of 1234). Is your page being protected by something in .htaccess?

Celebrate Intellectual Diversity

In reply to Re: WWW::Mechanize Problem by InfiniteSilence
in thread WWW::Mechanize Problem by pilgrim

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