Solution for TLang problem, (ab)using reader macros https://contest.tuenti.net/resources/2011/Question_2.html

tlang.lisp

(defun transform-expr (expr)
  (if (symbolp expr)
      (let ((s (symbol-name expr)))
        (cond ((string-equal s "=") '+)
              ((string-equal s "@") '-)
              (t expr)))
      expr))

(defun read-next-object (delimiter &optional (stream *standard-input*))
  (if (and delimiter (char= (peek-char t stream t nil t) delimiter))
      (and (read-char stream t nil t) nil)
      (read stream t nil t)))

(defun caret-reader (stream char)
  (declare (ignore char))
  (loop for object = (read-next-object #\$ stream)
     while object
     collect (transform-expr object) into objects
     finally (return `(format t "~a~%" (,@objects)))))

(defun read-delimiter (stream char)
  (declare (ignore stream char)))

(defun sharp-reader (stream char)
  (declare (ignore stream char))
  '*)

(set-macro-character #\^ #'caret-reader)
(set-macro-character #\$ #'read-delimiter)
(set-macro-character #\# #'sharp-reader)

(load *standard-input*)