Redirecting using VCL

If you, for some reason, don't want to redirect on the backend, but prefer to do it in VCL, you can do it using one of the following receipes:

Redirect if the user agent matches a regex

sub vcl_recv {
   if (req.http.user-agent ~ "iP(hone|od)") {
      error 750 "Moved Temporarily";
   }
}
 
sub vcl_error {
    if (obj.status == 750) {
        set obj.http.Location = "http://www.example.com/iphoneversion/";
	set obj.status = 302;
        deliver;
    }
}

Redirect if the user agent matches a regex (multiple sites)

sub vcl_recv {
   if (req.http.user-agent ~ "lwp") {
      if (req.http.host ~ "example.com") {
          error 750 "example.com";
      } else {
          error 750 "localhost";
      }
   }
}
 
sub vcl_error {
    if (obj.status == 750) {
        if (obj.response ~ "example.com") {
            set obj.http.Location = "http://www.example.com/customversion";
	} elsif (obj.response ~ "localhost") {
            set obj.http.Location = "http://localhost/customversion";
	}
	set obj.status = 302;
        deliver;
    }