Math::Pari doesn't work with 64-bit Windows. This is a very long standing issue, and it is mostly driven by not having an active maintainer. That isn't anyone's fault, since nobody is being paid to do it, and it sure doesn't look like a simple job. It works fine on *nix and MacOS, which means lots of devs and companies don't have much if any incentive.

KMX (Strawberry Perl dev) worked for quite a while on getting some alternatives for the common modules that rely on Math::Pari. A couple years ago it started shipping with some replacements for things like Crypt::RSA. Of course this doesn't help if you really want Math::Pari itself, but I suspect those people worldwide on Win64 could be counted in unary without taking off a shoe. Almost everyone, like yourself, just wants some other module that was written 10 years ago when Math::Pari was a quite reasonable (if not the only) choice.

As a module developer I find Strawberry Perl to be much nicer than ActiveState. A lot of that is just the model -- SP is much more like every other machine I use (Linux, FreeBSD, MacOS, AIX, Solaris, Cygwin, ...), while AS makes my life harder in trade for users not having a C compiler. I'm not thrilled that AS uses a weird beta MS compiler. My opinion might be different if I did simple pure-perl modules.