Desire to view contents of If-Modified-Since & If-None-Match http headers

For logging/modifying specific headers, I find that using a loop is usually the best way to parse through them:

when HTTP_REQUEST {
    set rqst_headers [HTTP::header names]
    set hsl [HSL::open -proto UDP -pool HIGH_SPEED_LOGGING]
    HSL::send $hsl "REQUEST HEADERS = $rqst_headers"
    foreach request_header [HTTP::header names] {
        if { $request_header eq "If-None-Match" } {
            HSL::send $hsl " $request_header = [HTTP::header values $request_header] "
        }
    }
}

The result should be that the If-None-Match header is logged along with the value using this format:

HEADER NAME = HEADER VALUE

Hope this helps!