;;; make a three element list
vars list =[1 2 3];

define test();
    ;;; dynamically scope the second element
    dlocal %hd(tl(list))%;
    [original list ^list]=>
    ;;; update second element
    5 -> hd(tl(list));
    [updated list ^list] =>
enddefine;

test();
** [original list [1 2 3]]
** [updated list [1 5 3]]

;;; But the value of hd(tl(list)) has been restored on exit:

list =>
** [1 2 3]