Financial calculations can be quite hairy AFAIK,

And for very good reasons.

They have special rounding rules and fixed precision like a tenth or hundreth of a cent.

Like

1 Euro = 1.95583 Deutsch Mark

But it's all integer in nature.

And bank rules may not be fiscal rules.

The only way I can think of to handle such systems transparently in Perl is using objects with overloaded operators. (With internal integers)