code: function defined_as() {
      var ret = this.seq(
          this.manyf(c_wsp),
          this.choicef(this.stringf('=/'), this.stringf('=')),
          this.manyf(c_wsp));
      return ret[2];
  }
docs: defined-as     =  *c-wsp ("=" / "=/") *c-wsp ; basic rules definition and ;  incremental alternatives