Read header into environment variable in Apache 2.2?

I want to process a request header using a custom rewrite map.

The开发者_C百科refore I want to have the content of the header in an environment variable.

I have not found a way to do that with mod_headers and/or mod_rewrite.

Any help is appriciated.

Mod_rewrite example for the request header "X-Forwarded-For":

RewriteRule .* - [E=X-Forwarded-For:%{HTTP:X-Forwarded-For}]