(letrec* ((*tree* '(#\t #\r #\e #\e #\o #\n #\e))
          (*forest* '(#\f #\o #\r #\e #\s #\t))
          (rep (lambda (t r)
                (let ((c (read-char)))
                 (cond
                    ((eof-object? c) r)
                    ((char=? c (car t)) (if (length=? t 1)
                                          (append *forest* (rep *tree* '()))
                                          (rep (cdr t) (append r (list c)))))
                    ((char=? c (car *tree*)) (append r (rep (cdr *tree*) (list c))))
                    (else (append r (list c) (rep *tree* '()))))))))
 (begin
   (for-each display (rep *tree* '()))
   (newline)))