EXAMPLES(例子)
                  下面这段代码和默认的配置相同,后端服务器主机名设置为“backend.exampl.com
                   backend default {
                    .host = "backend.example.com";
                    .port = "http";
                   }
 
                   sub vcl_recv {
                     if (req.http.x-forwarded-for) {
                     set req.http.X-Forwarded-For = req.http.X-Forwarded-For ", " client.ip;
                   } else {
                     set req.http.X-Forwarded-For = client.ip;
                   }
 
                   if (req.request != "GET" &&
                   req.request != "HEAD" &&
                   req.request != "PUT" &&
                   req.request != "POST" &&
                   req.request != "TRACE" &&
                   req.request != "OPTIONS" &&
                   req.request != "DELETE") {
                     // Non-RFC2616 or CONNECT which is weird.
                     return (pipe);
                     }
                   if (req.request != "GET" && req.request != "HEAD") {
                   // We only deal with GET and HEAD by default
                     return (pass);
                     }
                   if (req.http.Authorization || req.http.Cookie) {
                     // Not cacheable by default
                     return (pass);
                     }
                   return (lookup);
                   }
 
                   sub vcl_pipe {
                     # Note that only the first request to the backend will have
                     # X-Forwarded-For set.  If you use X-Forwarded-For and want to
                     # have it set for all requests, make sure to have:
                     # set req.http.connection = "close";
                     # here.  It is not set by default as it might break some broken web
                     # applications, like IIS with NTLM authentication.
                     return (pipe);
                   }
 
                   sub vcl_pass {
                     return (pass);
                   }
 
                   sub vcl_hash {
                     set req.hash += req.url;
                     if (req.http.host) {
                       set req.hash += req.http.host;
                     } else {
                       set req.hash += server.ip;
                     }
                     return (hash);
                   }
 
                   sub vcl_hit {
                     if (!obj.cacheable) {
                     return (pass);
                     }
                   return (deliver);
                   }
 
                   sub vcl_miss {
                     return (fetch);
                   }
 
                   sub vcl_fetch {
                   if (!beresp.cacheable) {
                     return (pass);
                   }
                   if (beresp.http.Set-Cookie) {
                     return (pass);
                     }
                   return (deliver);
                   }
 
                   sub vcl_deliver {
                     return (deliver);
                   }
 
                   sub vcl_error {
                   set obj.http.Content-Type = "text/html; charset=utf-8";
                   synthetic {"
                   <?xml version="1.0" encoding="utf-8"?>
                   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
                   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
                   <html>
                   <head>
                   <title>"} obj.status " " obj.response {"</title>
                   </head>
                   <body>
                   <h1>Error "} obj.status " " obj.response {"</h1>
                   <p>"} obj.response {"</p>
                   <h3>Guru Meditation:</h3>
                   <p>XID: "} req.xid {"</p>
                   <hr>
                   Varnish cache server
                   </body>
                   </html>
                   "};
                   return (deliver);
                   }
         下面的例子显示一个varnishd实例支持多个独立的站点,基于请求的URL选择使用的后端服务器:
                   backend www {
                     .host = "www.example.com";
                     .port = "80";
                   }
 
                   backend p_w_picpaths {
                     .host = "p_w_picpaths.example.com";
                     .port = "80";
                   }
 
                   sub vcl_recv {
                     if (req.http.host ~ "^(www.)?example.com$") {
                       set req.http.host = "www.example.com";
                       set req.backend = www;
                     } elsif (req.http.host ~ "^p_w_picpaths.example.com$") {
                       set req.backend = p_w_picpaths;
                     } else {
                       error 404 "Unknown virtual host";
                     }
                   }
 
                   The following snippet demonstrates how to force a minimum TTL for
                   all documents.  Note that this is not the same as setting the
                   default_ttl run-time parameter, as that only affects document for
                   which the backend did not specify a TTL:::
 
                   sub vcl_fetch {
                     if (obj.ttl < 120s) {
                     set obj.ttl = 120s;
                     }
                   }
         下面这段代码用来强制缓存带cookies的内容:
                   sub vcl_recv {
                     if (req.request == "GET" && req.http.cookie) {
                     call(lookup);
                     }
                   }
 
                   sub vcl_fetch {
                     if (beresp.http.Set-Cookie) {
                     deliver;
                    }
                   }
         下面代码的作用是利用squidHTTP PURGE模式清理无法使用的目标。
                   acl purge {
                     "localhost";
                     "192.0.2.1"/24;
                   }
 
                   sub vcl_recv {
                     if (req.request == "PURGE") {
                     if (!client.ip ~ purge) {
                       error 405 "Not allowed.";
                     }
                     lookup;
                     }
                   }
 
                   sub vcl_hit {
                     if (req.request == "PURGE") {
                       set obj.ttl = 0s;
                       error 200 "Purged.";
                     }
                   }
 
                   sub vcl_miss {
                     if (req.request == "PURGE") {
                     error 404 "Not in cache.";
                     }
                   }
         SEE  ALSO
                   Varnishd1
        
         HISTORY
                   The VCL language was developed by Poul-Henning Kamp in cooperation with Verdens       Gang AS, Linpro AS and Varnish Software. This manual page was written by Dag-Erling         Smørgrav and later edited by Poul-Henning Kamp and Per Buer.
        
         COPYRIGHT
         这个文档的版权和varnish自身的版本一样,请看LICENCE
                       * Copyright (c) 2006 Verdens Gang AS
                         * Copyright (c) 2006-2008 Linpro AS
                       * Copyright (c) 2008-2010 Redpill Linpro AS
                       * Copyright (c) 2010 Varnish Software AS