Nginx redirect load balancing

nginx.conf

http {
 
split_clients "${remote_addr}" $mirror {
	33%	"http://google.com";
	33%	"http://yahoo.com";
	*	"http://bing.com";
}
 
server {
	listen 0.0.0.0:80;
	listen [::]:80;
	server_name sub.domain.com www.sub.domain.com;
 
	location / {
		add_header X-Cache "Redirect load balancing";
 
		if ($http_referer = "") {
			set $mirror "http://duckduckgo.com";
		}
 
		return 302 $mirror;
	}
}
 
}