sub really_big_form {
    my $q = shift;

    my $sid;
    unless ($sid = $q->param('session')) {
        print_error('Get a session, loser');
        return;
    }

    unless ($session_vars{$sid}{new_style}) {
        respawn_session($sid);
        print_error('Old-style sessions are not cool, you are
        upgraded, go check your settings right now');
        return;
    }
    # ...
}

##</code><code>##

sub really_big_form {
    my $q = shift;

    my $sid = $q->param('session') or goto sub {
        print_error('Get a session, loser');
    };

    $session_vars{$sid}{new_style} or goto sub {
        respawn_session($sid);
        print_error('Old-style sessions are not cool, you are
        upgraded, go check your settings right now');
    };
    # ...
}