Why am I getting “called too early to check prototype” warnings in my Perl code?

Question

I have a Perl file like this:

use strict;
f1();

sub f3()
{ f2(); }

sub f1()
{}
sub f2()
{}

In short, f1 is called before it is d

Answer 1

When you define a function in Perl you should not use parentheses. When you do so you get this error. This is wrong:

sub DoSomthing(){
   #do what ever...
}

This is the way to go:

sub DoSomthing{
   #do what ever...
}

no parentheses.

For more detailed explenation see Gabor Szabo's Perl Maven page on Subroutines and functions in Perl. https://perlmaven.com/subroutines-and-functions-in-perl