(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)))))
                               (else (append r (list c) (rep *tree* '()))))))))
         (begin
           (for-each display (rep *tree* '()))
           (newline)))