Perl WWW::Mechanize Credentials - perl

Question

I want to search content from a site using WWW::Mechanize but to be able to do that first I must be logged in with my registered username and password, which I can't do with this code. What must be changed so I can submit the form successfully. Thanks.
use strict;
use warnings;
use WWW::Mechanize;
my $username = "username";
my $password = "password";
my $cookie_jar;
my $url = "http://www.albumartexchange.com/forums/ucp.php?mode=login";
my $mech = WWW::Mechanize->new( cookie_jar => $cookie_jar );
$mech->credentials($username, $password);
$mech->get($url);
$mech->success() or die "Failed";
$mech->submit_form(
form_number => 4,
);
die "Submit failed" unless $mech->success;
$mech->save_content('log.txt');
UPDATE:
use strict;
use warnings;
use WWW::Mechanize;
my $cookie_jar;
my $mech = WWW::Mechanize->new( cookie_jar => $cookie_jar );
$mech->get( 'http://www.albumartexchange.com/forums/ucp.php?mode=login' );
$mech->submit_form(
form_number => 4,
fields => {
'username'
=> 'some_username',
'password'
=> 'some_password',
}
);
$mech->save_content('log.txt');

Answer 1

You don't need credentials here. Just use:
$mech->submit_form(
form_number => 4,
fields => {
username => $user,
password => $pass,
},
);
Of course don't forget to change username and password to the actual field names for your target page.

Answer 2

That page doesn't use HTTP authentication, which is what credentials is for. Just use Mech to fill in the username and password form fields and submit the login form.