Is there a document on .rgs files syntax?

Resource scripts loaded from .rgs files are used with ATL CComModule::UpdateRegistryFromResource(). It's quite common to see samples of such files on the net but I've never seen a complete description on what constructs are 开发者_开发知识库allowed in .rgs files. Is there such a document?

There's some MSDN documentation, but it appears to be pretty unfocused.

The book ATL Internals talks at some length about custom replacements.

Other than that, I haven't seen much...