code: function () {
                      var curly, index = parserInput.i;
  
                      if (parserInput.currentChar() === '$' && (curly = parserInput.$re(/^\$\{([\w-]+)\}/))) {
                          return new(tree.Property)('$' + curly[1], index, fileInfo);
                      }
                  }
docs: A property entity useing the protective {} e.g. ${prop}