I wonder what compiler backend Vanilla/Strawberry perl uses - is it msvc- or cygwin-based?

It uses the MinGW port of the gcc compiler - and hence uses the msvc runtime library. Vanilla/Strawberry binaries (dll's) therefore work fine on ActivePerl (and vice-versa, for that matter).

However, as bart mentions elsewhere, you can use the very same MinGW port of gcc with ActivePerl anyway, if you want. (I don't think the performance issues you mentioned are significant, these days.)

If you're committed to building with ActivePerl, then the best option is to use Visual Studio 6.0. If you can't acquire that compiler, then the next best thing is to use the MinGW port of gcc. http://www.perlmonks.org/index.pl?node_id=614808 may be of some help.

I have also used Visual Studio 7.0 with ActivePerl without too much trouble - I don't think I'd even bother trying to use Visual Studio 8 with ActivePerl.

Cheers,
Rob