perl - What does the function declaration "sub function($$)" mean?

Question

I have been using Perl for some time, but today I came across this code:

sub function1($$)
{
   //snip
}

What does this mean in Perl?

Answer 1

It is a function with a prototype that takes two scalar arguments.

---

There are strong arguments for not actually using Perl prototypes in general - as noted in the comments below. The strongest argument is probably:

• Far More Than Everything You've Ever Wanted to Know about Prototypes in Perl

There's a discussion on StackOverflow from 2008:

• SO 297034

There's a possible replacement in the MooseX::Method::Signatures module.