Argument of spooler_process_after is undefined when language="javascript"

    <monitor  name="process0" ordering="0">
        <script  language="javascript">
            <![CDATA[
        function spooler_process_after(spooler_process_result){
            spooler_log.info('spooler_process_result='+spooler_process_result);
	    return spooler_process_result;
        }
            ]]>
        </script>
    </monitor>

spooler_process_result=undefined