How do I configure Plack to convert the contents of a request header to an environment variable

[Robert Rothenberg]

I am working on a Catalyst application that is accessed through a reverse proxy.  The proxy passes X-Proxy-REMOTE_USER header to the application. Is there a way to get Plack to take pass the content of the header to the REMOTE_USER environment variable in the Catalyst application?

[Ævar Arnfjörð Bjarmason]

Write a middleware to munge $env before the app gets to it.