&para;</a></span></dt>
<dd><p>By default, upon there being no more watches, timeouts and posted
events for an event loop, event-loop-run! will return, which is
normally what you want with a single threaded program.  However, this
is undesirable where a worker thread is intended to post an event to
the main loop after it has reached a result, say via
await-task-in-thread!, because the main loop may have ended before it
posts.  Passing #t to the val argument of this procedure will prevent
that from happening,