Can you show us your code? Most likely, you're running afoul of floating point precision errors, but that's hard to tell without seeing any of your code. Math::BigInt or Math::BigFloat might help, or maybe tye's Math::BigApprox. These all have different advantages and drawbacks, depending on your speed requirements and precision requirements. Note that it does not make sense to have a (much) higher precision in your result than in your input data.