my %cookies = CGI::Cookie->fetch;
my $score = $cookies{score}->value;
$score = 0 unless $score eq authenticated_score($score);

# (play game here, adding 1 to $score if this is a win)

log_winner() if $score >= 100;

$score     = authenticated_score($score);
my $cookie = CGI::Cookie->new(-name => 'score', -value => $score);
print header(-cookie=>$cookie);

# (send the rest of your HTML to the player.)