code: function () {
                      var name, nameLC, args, alpha_ret, index = i;
  
                      name = /^([\w-]+|%|progid:[\w\.]+)\(/.exec(current);
                      if (!name) { return; }
  
                      name = name[1];
                      nameLC = name.toLowerCase();
                      if (nameLC === 'url') {
                          return null;
                      }
  
                      i += name.length;
  
                      if (nameLC === 'alpha') {
                          alpha_ret = parsers.alpha();
                          if(typeof alpha_ret !== 'undefined') {
                              return alpha_ret;
                          }
                      }
  
                      $char('('); // Parse the '(' and consume whitespace.
  
                      args = this.arguments();
  
                      if (! $char(')')) {
                          return;
                      }
  
                      if (name) { return new(tree.Call)(name, args, index, env.currentFileInfo); }
                  }
docs: A function call  rgb(255, 0, 255)  We also try to catch IE's `alpha()`, but let the `alpha` parser deal with the details.  The arguments are parsed with the `entities.arguments` parser.