of course, you might want to handle a method that can return 0 by using defined

Or use the trick that some other modules use: return "0E0" or "0 but true" for zero, as a string. These are both true and 0, and do not produce warnings when converted into a number, the former because it's a normal floating point format, the latter because it's a hardcoded exception in perl.

Now I come to think of it: you can use any normal format for zero, as long as it's not "0", for example "0.0".