[users@httpd] modify Host header

[Eqbal Z]

I need to modify the Host header for my application in order to add the port
information.
I tried the following directive

RequestHeader set Host "%{HOST_NAME}e:443"

This sets it to (null):443

How do I get the host name value here? For example if the request comes in
as http://www.myhostname.com:8100/requested_resource
I am trying to get the www.myhostname.com part in the above directive by
using %{HOST_NAME}e

Any help is greatly appreciated.

Thanks.