Thanks for looking at all of that for me! I am glad to have someone tell me not to bother doing a bunch of extra work.

I will try doing that. Actually, maybe I'll use Devel::Peek for it. The thing about that huge number is that it's a custom big integer. It is created in AM.xs (grandtotal), and is an array of longs. In the XS normalize function it has a string and double representation added to it, and I suspected that it would be susceptible to overflow or something if the datatypes have the wrong bit size. Maybe I'll follow your advice on printing my suspicions and just add a ton of print statements in the XS, too.