How do I make private functions in a Perl module?

Question

I am working on a little Perl module and for some reason I had the test driver script that was using my new module call one of the functions that I thought would be private,

Answer 1

We can write some thing below in the perl private function to check whehter the call from the same obj as caller[0] gives package.

sub foo {
  my ($s, %args) = @_;
  die "Error: Private method called"
      unless (caller)[0]->isa( ref($s) );
}