P5NCI:

The name isn't great, the available thunks are too few, the known types are too simple, and it has a tendency to rebuild the C files every time you call ./Build, but P5NCI version 0.01 works and you're more than welcome to try it and send me patches.

Alternately, tell me how cool P5NCI::Library actually is in practice.

Thanks to jplindstrom for pointing me at Win32::API which already handles structs; I think I can modify that code to work on other platforms. What's a little sizeof between friends?