Tried you instructions for building on Windows - the IO-Compress tests all passed.

Thanks for taking the time to try it out, and also for the feedback.
I'll update that Issue 29 that you've created with improved information later today.

I think it must be something in my environment that's screwing things up ... or perhaps even this Windows 7 OS itself:

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.
[download]

In itself, it's not much of a problem if you're just building perl once.
But it does become quite a nuisance if you're building a number of perls with different configurations and/or with different versions of gcc.

Cheers,
Rob