There is UNIVERSAL, but adding methods to it is a generally bad idea, because you affect every class, and especially classes using AUTOLOAD can be tripped up by this.

Every Perl class has an implicit toString method, invoked by the print function. If you want to overload those, you likely want overload.

Even if you go the route of polluting UNIVERSAL, there is still the problem that 99.9% of the remaining Perl codebase doesn't know or support your variation.