Wait for one of the events to become signalled. Returns a pair of the form ( index . value ), where index, which is zero-based, identifies the signalled event, and value is the value associated with that event. The thread is suspended until at least one event becomes signalled. If an event has already been signalled at the time of the call to wait-multiple then the call returns immediately. As a convenience, any event may be a thread, in which case the thread's termination event is used.
It is often easier to use the select special form than calling wait-multiple directly.