5 has this. There are modules that get you to function signatures and type constraints. It's all opt-in and, as was said, you have to nudge LLMs to use it, but they can and the results are indeed better.
What kind of performance impact does it have? Obviously it depends on the specific program, but let's say the worst case scenario, something like a recursive implementation of the factorial function.
Minor. Faster unpacking of @_, but it's not a huge win until you have a lot of arguments. The conventional Perl 5 interpreter has no JIT to leverage the benefits of stronger types, inline functions, unroll loops, etc. A factorial function has few arguments, so the unpack gain will be small to nothing.
