Interestingly (for some definition of "interesting"), this also works and seems exactly equivalent (update: and reduces worries about phasing of BEGIN blocks, use statements and sub definitions, etc.):

c:\@Work\Perl\monks\Thenothing>perl -le
"use warnings;
 use strict;
 ;;
 use Mypackage;
 ;;
 print Mypackage::test2();
 ;;
 print test();
"
hiya @ Wed Apr 11 12:35:25 2018
hiya @ Wed Apr 11 12:35:25 2018
[download]

File Mypackage.pm:

package Mypackage;

use warnings;
use strict;

sub main::test { return 'hiya @ ' . localtime; }

sub test2 { ::test(); }

1;
[download]

Oh, and by the way: Don't Do This! Others have suggested much better ways of organizing your code.