sub_recv.vcl

sub vcl_recv {
    // remove jquery cache buster query parameter if it exists
    if (req.url ~ "_=[0-9]+") {
        set req.http.clean = regsuball(req.url, "(_=[0-9]+)", "");
        set req.http.clean = regsub(req.http.clean, "\?&", "?");
        set req.http.clean = regsub(req.http.clean, "&&",  "&");
        set req.http.clean = regsub(req.http.clean, "&$",  "");
        set req.http.clean = regsub(req.http.clean, "\?$", "");
        // modify the url with the clean version
        set req.url = req.http.clean;
    }
}