The solution should be CPAN grade.

Frankly, I would say that before you do anything else you should use that “C compiler that has no problems with 64-bit ints” to compile a version of Perl.   In other words, sidestep completely the issue of providing a 64-bit quantity to a Perl that can’t handle it.
........................
These days you can run 64-bit ints just as easily as you can run 32-bit; therefore, do so.

I understand you're being frank. 64 bit Windows users are currently a minority, http://www.itsnyc.com/index.php/blog/item/windows-7s-64-bit-adoption. I think you know the status and support of Perl 32 bit pointers with 64 bit ints on Windows.