skip t/fork.t on MSWin32 (and Cygwin):
Win32 threads (and fork() is emulated via threads) in the
same process share the same STDIN/STDOUT/STDERR, hence
the method used by run3() (redirect STD* and then call system())
doesn't work here and IO crossover is to be expected -
a possible alternative on Win32 would be to use CreateProcess
which lets you explicitly specify three filehandles for the
new process' STDIN/STDOUT/STDERR; however Win32::Process::Create()
(from the libwin32 CPAN distribution) as omitted these
parameters from the Perl wrapper
add a note to the documentation about the problems with
concurrent calls to run3 in a threaded environment
(incl. fork() on Win32)
make sure all tests run with warnings on