Your description is vague. You don't tell us the value of $col2. You don't give us CALCUL_DIV. You don't tell us how you print the results. You don't tell us which version of Perl, or which size integers/reals it's using.

It's most likely a rounding issue, with CALCUL_DIV returning a very small value - which if it gets multiplied by -1 will be printed as "-0". But without more details, it's hard to pinpoint where it happens, and how to prevent it.

Could you post a self contained program that prints "-0" where you expect "0"?

Abigail