The example code for EVENTEXTRA won't syntax check. It needs to be changed to:

    doMyService := FUNCTION
      O := OUTPUT('Did a Service for: ' + 'EVENTNAME=' + EVENTNAME);
      N := NOTIFY(EVENT('MyServiceComplete',
                   '<Event><returnTo>FRED</returnTo></Event>'),
                  EVENTEXTRA('returnTo'));
      RETURN WHEN(EVENTEXTRA('returnTo'),ORDERED(O,N));
    END;
    OUTPUT(doMyService) : WHEN('MyService');

    // and a call (in a separate workunit):
    NOTIFY('MyService',
           '<Event><returnTo>'WORKUNIT'</returnTo></Event>');
    WAIT('MyServiceComplete');
    OUTPUT('WORKUNIT DONE')