add name or list of names to the list of untouchable symbols

(push-untouchable my-var nil)
(push-untouchable set-mem t)

General Form:
(push-untouchable name{s}  fn-p :doc doc-string)
where name{s} is a non-nil symbol or a non-nil true list of symbols, fn-p is any value (but generally nil or t), and doc-string is an optional documentation string not beginning with ``:Doc-Section ...''. If name{s} is a symbol it is treated as the singleton list containing that symbol. The effect of this event is to union the given symbols into the list of ``untouchable variables'' in the current world if fn-p is nil, else to union the symbols into the list of ``untouchable functions''. This event is redundant if every symbol listed is already a member of the appropriate untouchables list (variables or functions).

When a symbol is on the untouchables list it is syntactically illegal for any event to call a function or macro of that name, if fn-p is non-nil, or to change the value of a state global variable of that name, if fn-p is nil. Thus, the effect of pushing a function symbol, name, onto untouchables is to prevent any future event from using that symbol as a function or macro, or as a state global variable (according to fn-p). This is generally done to ``fence off'' some primitive function symbol from ``users'' after the developer has used the symbol freely in the development of some higher level mechanism.

Also see remove-untouchable.