public Parser controlPhrase() {
        if (controlPhraseParser == null) {
           FutureParser future = scoped("controlPhrase");
           controlPhraseParser = future;
           future.setParser(
               sequence(
                   token("CONTROL"),
                   optional(
                       token("IS")
                   ),
                   choice(
                       identifier_format2(),
                       literal()
                   )
               )
           );
        }

        return controlPhraseParser;
    }