examples of special variables

(defun make-lexical-printer (value)
  (lambda ()
    (print value)))

(let ((printer (make-lexical-printer 78)))
  (funcall printer)) ; prints 78

(defun make-special-printer (value)
  (declare (special value))
  (lambda ()
    (print value)))

(let ((printer (make-special-printer 89)))
  (funcall printer)) ; error, value is unbound

(let* ((value 23)
       (printer (make-special-printer 89)))
  (funcall printer)) ; error, value is unbound

(let* ((value 23)
       (printer (make-special-printer 89)))
  (declare (special value))
  (funcall printer)) ; prints 23