NAME Acme::Signature::Arity - provides reliable, production-ready signature introspection DESCRIPTION You'll know if you need this. If you're just curious, perhaps start with https://www.nntp.perl.org/group/perl.perl5.porters/2021/11/msg262009.html. No part of this is expected to work in any way when given a sub that has a prototype. There are other tools for those: Sub::Util. For subs that don't have a prototype, this is also not expected to work. It might help demonstrate where to look if you wanted to write something proper, though. Exported functions arity Returns the UNOP_aux details for the first opcode for a coderef CV. If that code uses signatures, this might give you some internal details which mean something about the expected parameters. Expected return information, as a list: * number of required scalar parameters * number of optional scalar parameters (probably because there are defaults) * a character representing the slurping behaviour, might be '@' or '%', or nothing (undef?) if it's just a fixed list of scalar parameters This can also throw exceptions. That should only happen if you give it something that isn't a coderef, or if internals change enough that the entirely-unjustified assumptions made by this module are somehow no longer valid. Maybe they never were in the first place. max_arity Takes a coderef, returns a number or undef. If the code uses signatures, this tells you how many parameters you could pass when calling before it complains - undef means unlimited. Should also work when there are no signatures, just gives undef again. min_arity Takes a coderef, returns a number or undef. If the code uses signatures, this tells you how many parameters you need to pass when calling - 0 means that no parameters are required. Should also work when there are no signatures, returning 0 in that case. AUTHOR TEAM@cpan.org WARRANTY None, it's an Acme module, you shouldn't even be reading this.