code: function() {
                      var c = input.charCodeAt(i);
                      if ((c > 57 || c < 45) || c === 47) return;
                      var value = $(/^(-?\d*\.?\d+(?:[eE][-+]?\d+)?)(\%|\w+)?/);
                      if (value) {
                          return new tree.Dimension(value[1], value[2], memo, env.filename);
                      }
                  }
docs: A Dimension, that is, a number and a unit. The only unit that has an effect is %