gistfile1.lisp

(defun a-bound-p ()
  (boundp 'a))

(defun funcall-with-a-as-special-variable (function &optional a)
  (declare (special a))
  (funcall function))

(funcall-with-a-as-special-variable
  #'a-bound-p) ;;; => T

(let ((a 5))
  (a-bound-p)) ;;; => NIL