(set symbol value) ≡ (setf (symbol-value symbol) value)

 (setf (symbol-value 'n) 1) ⇒  1
 (set 'n 2) ⇒  2
 (symbol-value 'n) ⇒  2
 (let ((n 3))
   (declare (special n))
   (setq n (+ n 1))
   (setf (symbol-value 'n) (* n 10))
   (set 'n (+ (symbol-value 'n) n))
   n) ⇒  80
 n ⇒  2
 (let ((n 3))
   (setq n (+ n 1))
   (setf (symbol-value 'n) (* n 10))
   (set 'n (+ (symbol-value 'n) n))
   n) ⇒  4
 n ⇒  44
 (defvar *n* 2)
 (let ((*n* 3))
   (setq *n* (+ *n* 1))
   (setf (symbol-value '*n*) (* *n* 10))
   (set '*n* (+ (symbol-value '*n*) *n*))
   *n*) ⇒  80
  *n* ⇒  2
 (defvar *even-count* 0) ⇒  *EVEN-COUNT*
 (defvar *odd-count* 0) ⇒  *ODD-COUNT*
 (defun tally-list (list)
   (dolist (element list)
     (set (if (evenp element) '*even-count* '*odd-count*)
          (+ element (if (evenp element) *even-count* *odd-count*)))))
 (tally-list '(1 9 4 3 2 7)) ⇒  NIL
 *even-count* ⇒  6
 *odd-count* ⇒  20