package Drone;
sub new { return bless {}, shift; }
1;

package Factory;
no strict 'refs';
sub fixup {
    #*Drone::bar = sub { return __PACKAGE__ };
    my $class = shift || __PACKAGE__;
    *Drone::bar = sub { return $class };
}
1;

package Subfactory;
use base qw( Factory );
1;

package main;
Subfactory->fixup;
my $foo = Drone->new;
print $foo->bar . "\n";