squo;thunk&rsquo; throws and its return value will
be the return value of this procedure; otherwise the program will
terminate if an unhandled exception propagates out of &rsquo;thunk&rsquo;.
&rsquo;handler&rsquo; should take the same arguments as a guile catch handler
(this is implemented using catch).
</p>
<p>This procedure must (like the a-sync procedure) be called in the same
thread as that in which the default glib main loop runs, where the
result of calling &rsquo;thunk&rsquo; will be received.  As me