device-detect

sub vcl_recv {
        if (req.url ~ "\.(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|pdf|txt|tar|wav|bmp|rtf|js|flv|swf)$") {
                set req.http.X-Device = "NA";
        } else {
                call identify_device;
        }
}

sub identify_device {
	if (req.http.User-Agent ~ "mobileapp" ) {
    		set req.http.X-Device = "mobileapp";
	} else {
    		set req.http.X-Device = "PC";
	}
}

sub vcl_deliver {
        if (req.http.X-Device != "NA") {
               if (resp.http.Vary) {
                       set resp.http.Vary = resp.http.Vary + "," + "User-Agent";
               } else {
                       set resp.http.Vary = "User-Agent";
               }
        }
}

sub vcl_hash {
        hash_data(req.http.X-Device);
}