(defun player-turn2 (board)
  (format t "Please enter X: ")
  (let ((x (parse-integer (read-line) :junk-allowed t)))
    (unless (member x '(0 1 2))
      (player-turn2 board))
    (format t "~a~%" x)))


Please enter X: 4
Please enter X: 3
Please enter X: 2
2
3
4
NIL