formation about headers
    cookies, context, request or session attributes and request
    parameters.
    </p>
    <ul>
    <li><b><code>cs(XXX)</code></b> for incoming request headers with name XXX</li>
    <li><b><code>sc(XXX)</code></b> for outgoing response headers with name XXX</li>
    <li><b><code>x-A(XXX)</code></b> for the servlet context attribute with name XXX</li>
    <li><b><code>x-C(XXX)</code></b> for the first cookie with name XXX</li>
    <li><b><code>x-O(XXX)</code></b> for a concatenati