# ...

$action = $query->param('action');
$voted = hasuservoted();

if ($action eq "show")
    $voted ? show_results() : show_poll();
}
elsif ($action eq "vote" && !$voted) {
    vote();
}
else {
    error("no valid action");
}

sub show_poll {

    # display the poll so the user can fill it in.

}

sub show_results {

    # show the poll results -- user can no longer vote

}

sub vote {
    
    # record the user's vote
    # record who voted
    # redirect to index.shtml
}

sub hasuservoted {

    # returns 1 if user has voted
    # returns 0 if user has no voted

}