sub setup {
        my $self = shift;
        $self->start_mode('mode1');
        $self->mode_param('rm');
        $self->run_modes(
                'mode1' => 'do_stuff',
                'mode2' => 'do_more_stuff',
                'mode3' => 'do_something_else'
        );
  }

##</code><code>##

if    ($cgi{rm} eq 'mode1') { do_stuff }
 elsif($cgi{rm} eq 'mode2') { do_more_stuff }
 ...