ply s p t hs transform &gt;&gt; heartbeat m w jn rn) (do
                        -- &quot;don't forget to unregister!&quot; (Frank Zappa)
                        sc &lt;- unRegister c jn wn rn tmo
                              unless (sc == OK) $ 
                                throwIO $ NotOKX sc &quot;on unregister&quot;)
        -- not ok ---------------------------
        e -&gt; throwIO $ NotOKX e &quot;on register&quot;
</pre><p>There is, however, a function that does all of this internally: 
     <