code: function () {
                      var name, index = parserInput.i;
  
                      if (parserInput.currentChar() === '$' && (name = parserInput.$re(/^\$[\w-]+/))) {
                          return new(tree.Property)(name, index, fileInfo);
                      }
                  }
docs: A Property accessor, such as `$color`, in  background-color: $color