如果存在 cookie，Nginx 重定向

我看到了一些关于使用 Nginx 检查 cookie 的有限资源，但我真的找不到我想要的答案，希望你们中的一些 Nginx 高手可以帮助我.

I've seen some limited resources on checking for cookies with Nginx, but I couldn't really find the answer I was looking for, hopefully some of you Nginx masters can give me a hand.

基本上我有一个虚拟主机，我想重定向到不同的域，除非用户有 cookie，这是我创建的:

Essentially I have a vhost that I'd like to redirect to a different domain unless the user has a cookie, here is what I've created:

server {
  listen 80;
  server_name example.com;

  if ($http_cookie ~* "dev_cookie" ) {
    root /home/deploy/apps/example/current/public;
    passenger_enabled on;
    rack_env production;
    break;
  }
  rewrite ^/(.*) http://beta.example.com/$1 permanent;
}

但它似乎不起作用，我收到错误消息:

But it doesn't seem to work, I get the error:

[emerg]: "root" directive is not allowed here in /opt/nginx/conf/nginx.conf:45

我不知道如何在这里进行，各位有什么想法吗?

I'm not sure how to proceed here, any ideas guys?