shift-click, control-click, and alt-click

[Robert Ringrose]

How can I check for a combination of, say, shift and a mouse button?
(alt and/or control would be nice, too)

Checking for an individual mouse button is easy: getbutton(LEFTMOUSE)
Checking for a normal keyboard event is about as easy.  Unfortunately,
shift, control, and alt aren't quite normal keyboard events.  Ideas?

Thanks in advance,

	- Robert Ringrose
	ringrose at ai.mit.edu

"There's always one more bu6."