At least on my Perl 5.8.5 and Perl 5.9.2 (some recent sync), the segfault occurs under Win32 as well. The code you referenced is fairly long, so I don't directly see what might be causing this. The perl.com link you referred to does not seem to imply in any case that there was any bugfix - the section "Perl Threads" only describes the move from the really broken threading model to a model with different bugs.

If Interchange relies on threads, I would not use it, but you might have other reasons that outweigh the pain of Perl threads.

In any case, I think it would pay off to reduce this program to a small program of about 50 lines or something, and then report that bug via the perlbug utility, so the right people see it.

Update: From the first looks, it seems like your threads are playing tag-team on the FILE - I don't think that this will really work, even if the crash is removed ...