This module performs DoubleDouble arithmetic. To use it, make sure that you have installed: gmp-6.2.0 or later ( https://gmplib.org ) mpfr-4.1.0 or later ( https://www.mpfr.org ) Then install Math::MPFR-4.22 or later: cpan -i Math::MPFR Then install this module: cpan -i Math::FakeDD Please raise any issues with Math::MPFR at: https://github.com/sisyphus/math-mpfr/issues Please raise any issues with Math::FakeDD at: https://github.com/sisyphus/math-fakedd/issues The basics of the DoubleDouble data type and its arithmetic can be found at: https://en.wikipedia.org/wiki/Quadruple-precision_floating-point_format#Double-double_arithmetic