Thanks syphilis for your comment !

I have looked into all suggestions and learned a lot ! Thanks to all !

One question to Math::BigFloat, Math::Decimal and Math::Decimal64 :

* Is this correct: As soon as at least one variable in an expression is a Math object (e.g. MEtoD64 after use Math::Decimal64 qw/:all/;) the calculation is done with the Math-functions, not with the standard functions. If there is no Math object in the expression, the calculation is still done with the fast standard functions. So I can use both (accurate and fast arithmetic) on the contrary when I use "use bignum", where I always use the accurate Math functions for all operations.

* How can I check if a variable is a standard scalar or a Math object (like "ref" for hash/array)?

* Is there a good overview document, pointing out the differences between Math::BigFloat, Math::Decimal, Math::Decimal64, Math::BigInt and Math::BigRat. (When to use which library best?)