I don't think it's undefined, I think it's indeterminate form. By definition, anything to the 0 power is 1. In calculus it becomes meaningless, but in Perl it doesn't cause an error.
The wiki you refer to seems to be bit clumsy there. Rather than be meaningless in calculus, I would argue that calculus, a branch of mathematical analysis, is the only discipline known to be capable of giving such values a meaning.