my $win = 0;
my $i = 0;
do {
     $i += 1;
     printf "Player %d's turn:\n",2-$i%2;
   # game code here
   # when a winning move is detected:
     $win = 1;
} until (($win) || ($i == 9));
printf "%s won\n", $win ? sprintf "Player %d",2-$i%2 : "Nobody";