Adding custom header with URL/method etc. information

Hi,

I need to add custom header into requests with some information about currently processing request. I'm looking at reqadd parameter, but the string looks like a static text. I would need something like that:

    reqadd X-Original-URL:\ $HTTP_URL_ABS

Now the header is added as is written.

Many thanks for any help,
vl

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Vlastimil Holer
Operations Engineer
www.gooddata.com
+420 5 3050 7711