in reply to
Adding really big numbers

Which version of Perl are you using? It works just fine for me on 5.16.1. Using bigint, I get values for every integer. Using bignum, I get values for every int and decimal (except for trailing zeroes). Without an extra module, anything over 20 digits defaults to scientific notation with 15 digits of precision.

*Update: Here is some info on largest positive/negative integers that can be nadled by different setups w/o using modules: Re: maximum value of a scalar*