As already noted, these "parameter specifications" are called "prototypes", but they have absolutely nothing to do with function prototypes in C. They are also generally best avoided.

If you want something similar to C's function prototypes (parameter type/number checking, plus support for optional and/or named parameters), take a look at Devel::Declare for the general case or MooseX::Declare if you're doing Moose-based OO.