gistfile1.txt

<VirtualHost *:80>
  ServerAlias *.domain.com
  RewriteEngine on
  Rewritemap domaintoport prg:/home/user/rewrite_map/rewrite_map
  # RewriteCond %{HTTP_HOST} (.*)
  RewriteRule (.*) http://localhost:${domaintoport:%{HTTP_HOST}}/$1 [P]

  ProxyRequests Off
  <Proxy *>
    AddDefaultCharset off
    Order deny,allow
    Allow from all
  </Proxy>

#  ProxyPreserveHost On

#  ProxyPass / http://localhost:4000/
#  ProxyPassReverse / http://localhost:4000/

</VirtualHost>