public Parser capitalizationPhrase() {
        if (capitalizationPhraseParser == null) {
           FutureParser future = scoped("capitalizationPhrase");
           capitalizationPhraseParser = future;
           future.setParser(
               choice(
                   token("UPPER"),
                   token("LOWER")
               )
           );
        }

        return capitalizationPhraseParser;
    }