package MyApp::Base;
use base 'CGI::Application';
sub cgiapp_init {
  my $self = shift;

  # init your application: session, database, whatever is needed
  ...

  # set the name of the run mode CGI param
  $self->mode_param('rm');

  # shared run modes
  $self->run_modes('login'    => 'login',
                   'AUTOLOAD' => 'autoload_exception');

  return;
}

...
sub session { return shift->param('SESSION'); }
...

sub cgiapp_prerun {
  my $self = shift;
  my $runmode = shift;
  my $user = $self->session->param('user');
  unless ($user) {
    $self->prerun_mode( 'login' );
  }
}

##</code><code>##

package MyApp::Application1;
use base 'MyApp::Base';
...