code: function() {
      var captures;
      if (captures = /^(true|false)\b([ \t]*)/.exec(this.str)) {
        var val = nodes.Boolean('true' == captures[1]);
        this.skip(captures);
        var tok = new Token('boolean', val);
        tok.space = captures[2];
        return tok;
      }
    }
docs: 'true' | 'false'