code: function rule() {
      var ret = this.seq(rulename, defined_as, elements, c_nl);
  
      var da = ret[2];
      if (da === "=") {
          return this.rules.addRule(ret[1], ret[3]);
      }
      if (da === "=/") {
          return this.rules.addAlternate(ret[1], ret[3]);
      }
      return this.fail();
  }
docs: rule           =  rulename defined-as elements c-nl ; continues if next line starts ;  with white space