package AAA;
use 5.20.1;
use lib ('.');
use BBB;
use parent('Exporter');
our @EXPORT=('$bbb','$msg');
our $bbb=BBB->new();
return 1;

package BBB;
use 5.20.1;
use lib '.';
use AAA;
sub new{
    my $class=shift;
    my $self=bless {},$class;
    return $self;
}
sub hello{
    my $self=shift;
    say 'hello';
}
sub hello2{
    my $self=shift;
    $bbb->hello();
}
return 1;

package main;
use 5.20.1;
use lib ('.');
use AAA;
$bbb->hello2();


perl test.pl
Global symbol "$bbb" requires explicit package name at BBB.pm line 16.
Compilation failed in require at AAA.pm line 4.
BEGIN failed--compilation aborted at AAA.pm line 4.
Compilation failed in require at test.pl line 4.
BEGIN failed--compilation aborted at test.pl line 4.