KEYACT							(variable)

	if nonempty, should be an instruction list that will be evaluated
	whenever a key is pressed on the keyboard.  The instruction list
	can use READCHAR to find out what key was pressed.  Note that only
	keys that produce characters qualify; pressing SHIFT or CONTROL
	alone will not cause KEYACT to be evaluated.

	Note that it's possible for the user to press a key during the
	evaluation of the instruction list.  If this would confuse your
	program, prevent it by temporarily setting KEYACT to the empty
	list.  One easy way to do that is the following:

		make "keyact [key.action]

		to key.action [:keyact []]
		... ; whatever you want the key to do
		end