After installing this tool you can specify redirections inside of your CMF portal, similar to the way as Apache Rewrite rules works.
The match and replacement patterns are all regular expressions, and you can select which HTTP status code to return.
I couldn't for the life of me figure out how to make it work with virtual hosting. The URL rewriting engine takes a URL relative to the parent of the tool (usually the portal root), but I don't know how to get that relative URL in a virtual hosting environment; I tried quite a few ways.
Help welcome.