package TwoFer;
use strict;
use warnings;
use Exporter qw<import>;
our @EXPORT_OK = qw<two_fer>;

sub two_fer {
  my ($name) = @_;
  return "One for " . ($name ? $name : 'you') . ", one for me.";
}

1;

__END__
If you are using perl v5.20 or newer, you
can replace the existing sub declaration
with the following code:

use experimental qw(signatures);

sub two_fer ($name = undef) {}

1;