code: function () {
                  var a, b;
  
                  if (! peek(/^[@\w.%-]+\/[@\w.-]+/)) return;
  
                  save();
  
                  if ((a = $(this.entity)) && $('/') && (b = $(this.entity))) {
                      return new(tree.Shorthand)(a, b);
                  }
  
                  restore();
              }
docs: A font size/line-height shorthand  small/12px  We need to peek first, or we'll match on keywords and dimensions