title: Why throw an exception in the unexpected handler?
body: <p>I have seen many code examples where the <code>unexpected()</code> function handler (as set by <code>set_unexpected</code>) itself throws an exception.</p>
  <p>What is the point of doing that?  I thought <code>unexpected()</code> was the exception catcher of last resort.  Who will catch the exception thrown by the <code>unexpected()</code> function handler?</p>