anchor.diff:        (lambda (list)
           (cond ((eql (car list) :mval)
                  (error "nested :MVAL in ~A are meaningless" vars))
  -              ((member (car list) *binder-specs*)
  -               (let ((var-name (gensym (format nil "~A-" (car list)))))
  +              ((or extract-plain-lists (member (car list) *binder-specs*))
  +               (let ((var-name (gensym (if extract-plain-lists
  +                                           "LIST-"
  +                                           (format nil "~A-" (car list))))))
                    (push (cons list var-name) bindings)
                    (values nil var-name)))
                 (t (values t list)))))
  
positive.code:        (not (null symbol))
         (not (keywordp symbol))))
  
  (defun extract-nested-binding-specs (vars decls)
    (let ((bindings nil))
      (values
       (map-lambda-list
  
negative.code: 
    (define-binder (:mval (var list) val decls body)
      (multiple-value-bind (vars bindings)
          (extract-nested-binding-specs var decls :extract-plain-lists t)
        `(multiple-value-bind ,vars ,val
           ,@(when-let (decl (mapcan (lambda (x) (use-declaration x decls)) vars))
                       `((declare ,@decl)))
  