anchor.diff:  
   (defmacro define-command (name parms &body body)
     `(setf (gethash ',name *command-table*)
  -         #'(lambda ,parms ,@body)))
  +         #'(lambda ,parms (declare (ignorable ,@parms)) ,@body)))
   
   (defun call-command (cmd arg)
     (funcall (gethash cmd *command-table*) arg))
  
positive.code: (define-command :cd (arg)
    (uiop:chdir arg))
  
  (define-command :pwd (arg)
    (declare (ignore arg))
    (uiop:getcwd))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  
negative.code:          (pathname-length (length (namestring path))))
      (loop
        :for pathname :in (cl-fad:list-directory path)
        :for name := (enough-namestring pathname path)
        :when (eql 0 (search text name))
        :collect name)))
  
  