parsing funny notation

(define-matcher uppercase (in #\A #\Z))
(define-matcher numerals (in #\0 #\9))

(defun read-bracket ()
  "Reads fragments of funny notation inside brackets"
  (consume)
  (loop for next = (peek)
        while (and next (char/= next #\]))
        collect (read-piece)
        finally (consume)))

(defun read-piece ()
  "Reads a fragment of funny notation up to a landmark (rN rNN cpR4, up to a capital letter + opt. digit)"
  (let ((tag (consume-until (make-matcher (or :uppercase (any #\[ #\])))))
        (next (peek)))
    (format t "~a & ~s, " tag next)
    (case next
      (#\[ (cons tag (read-bracket)))
      (#\] tag)
      ;; Issue: reader consumes too many repeated letters ("WWW" doesn't get parsed into "WW" "W")
      (T (format NIL "~a~:[~;~:*~a~]" tag (consume-until
                                           (make-matcher
                                            (not
                                             (or (is (string next)) :numerals)))))))))

(defun funny-notation->parsed-fragments (string)
  (with-lexer-environment (string)
    (loop while (peek)
          collect (read-piece))))