http://www.perlmonks.org?node_id=845972


in reply to Math::BigInt: couldn't load specified math lib(s), fallback to Math::BigInt::Calc at /usr/lib/perl5/site_perl/5.8.8/Crypt/DH.pm line 6

It just tells you that it couldn't find the C lib so it falls back to the pure Perl implementation for the calculations. Solution is to find which lib is missing or not in the path and link it properly to the module.