how to dynamically set a request header befor send the content handler is run

["Liudonghua (Eric)" <eric.liudonghua@xxxxxxxxxx>]

I have already read the mod_headers configure document (http://httpd.apache.org/docs/2.4/mod/mod_headers.html).

And I see early requestheader maybe solve my problem.

RequestHeader add|append|edit|edit*|merge|set|unset header [value] [replacement] [early|env=[!]variable]|expr=_expression_]

For my requirement that I need to change a request header before the following operation.

For example, a HTTP request contains a header headerName:headerValue. And now I should convert it to NewHeaderName:NewHeaderValue which NewHeaderValue is depend on the headerValue.

Because early and expr=_expression_ in the requestheader syntax can not use together.

How can I achieve this goal.

Thanks in advance.