Apache: how to rewrite request headers

Wonderful solution from http://www.kahunaburger.com/2012/05/18/mod_rewrite-and-mod_headers-to-rewrite-headers/

Thanks a lot !

LoadModule rewrite_module modules/mod_rewrite.so
LoadModule headers_module modules/mod_headers.so

RewriteEngine On

# all /foo/bar urls set env vars FIRST=foo and SECOND=bar
RewriteRule ^/([^/]+)/([^/]+) - [E=FIRST:$1,E=SECOND:$2]

# rewrite all /foo/bar to /cgi-bin/printenv.pl/foo/bar
RewriteRule ^/([^/]+)/([^/]+) /cgi-bin/printenv.pl/$1/$2 [PT]

# if env var FIRST is set then create header First: $ENV{FIRST}
RequestHeader set First %{FIRST}e env=FIRST

# if env var SECOND is set then create header Second: $ENV{SECOND}
RequestHeader set Second %{SECOND}e env=SECOND

Using this, any URL of the form http://server.com/foo/bar would be rewritten to http://server.com/cgi-bin/printenv.pl/foo/bar and if you inspect the HTTP headers during printenv.pl you would find the headers "First: foo" and "Second: bar". Hope somebody else finds it useful.