如何在OOZIE中使用正则表达式？

<workflow-app name="regex-example" xmlns="uri:oozie:workflow:0.5">
    <start to="regex-action" />
    <action name="regex-action">
        <shell xmlns="uri:oozie:shell-action:0.3">
            <job-tracker>${jobTracker}</job-tracker>
            <name-node>${nameNode}</name-node>
            <exec>script.sh</exec>
            <argument>${input}</argument>
            <argument>${output}</argument>
        </shell>
        <ok to="end" />
        <error to="fail" />
    </action>
    <kill name="fail">
        <message>Regex action failed, error message[${wf:errorMessage(wf:lastErrorNode())}]</message>
    </kill>
    <end name="end" />
</workflow-app>