I've been dealing with forms for well over two years and I am still very happy doing manual checks on data, without any module help. You simply create a subroutine that outputs your form and do something like the following:

# login.pl:
#!c:/perl/bin/perl -w
$|++;

use CGI::Simple;
use Template;

my $CGI = CGI::Simple->new;

my $TMPL = Template->new( {
   INCLUDE_PATH => '/path/to/templates'
} );

my $user = $CGI->param('user') || '';
my $pass = $CGI->param('pass') || '';

form_login('Please enter your member ID and password:')
   if ( ($user eq '') || ($pass eq '') );

form_login('Invalid member ID/password combination.')
   unless ( some_auth_method($user, $pass) );

# authentication successfull
auth_successfull(do => 'something', now => 'please');


sub form_login {
   my ($usermsg) = @_;

   print $CGI->header();

#   $TMPL->process('login.tmpl', {
   $TMPL->process(\*DATA, {
      $CGI->Vars(' '),

      title   => 'Member Login',
      usermsg => $usermsg
   } );

   exit;
}

__DATA__
[% USE HTML %]
[% INCLUDE header.tmpl %]

<p>[% HTML.escape(usermsg) %]</p>

<form action="/path/to/login.pl" method="post">
   Member ID: <input type="text"
                     name="user"
                     value="[% HTML.escape(user) %]"
                     size="20"
                     maxlength="15" /><br /><br />

   Password: <input type="password"
                    name="pass"
                    value="[% HTML.escape(pass) %]"
                    size="20"
                    maxlength="20" /><br /><br />
   <input type="submit" value="login now" />
</form>

[% INCLUDE footer.tmpl %]
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