title: http_sub_module / sub_filter of nginx and reverse proxy not working
body: <p>I am trying to reverse proxy my website and modify the content.
  To do so, I compiled nginx with sub_filter.
  It now accepts the sub_filter directive, but it does not work somehow.</p>
  
  <pre><code>server {
      listen       8080;
      server_name  www.xxx.com;
  
      access_log  /var/log/nginx/www.goparts.access.log  main;
      error_log  /var/log/nginx/www.goparts.error.log;
      root   /usr/share/nginx/html;
      index  index.html index.htm;
  
      ## send request back to apache1 ##
      location / {
         sub_filter &lt;title&gt; '&lt;title&gt;test&lt;/title&gt;';
   sub_filter_once on;
  
  
       proxy_pass  http://www.google.fr;
       proxy_next_upstream error timeout invalid_header http_500 http_502 http_503 http_504;
       proxy_redirect off;
       proxy_buffering off;
       proxy_set_header        Host            $host;
       proxy_set_header        X-Real-IP       $remote_addr;
       proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
  
     }
  }
  </code></pre>
  
  <p>Please help me</p>