The only thing that makes sense for a "Bizarre SvTYPE (17)" is memory getting overwritten, which would be a bug in Perl (unless you are heavilly abusing pack/unpack).

But fork under Win32 is pretty fragile so I'm not that surprised that using it can result in memory corruption. I encourage you to report it using "perlbug".

You can do some moderately ugly hacks like (tye)Re: How to multiprocess in Win32? to get around many needs for fork under Win32.

        - tye (but my friends call me "Tye")