How to avoid extra DESTROY calls in multi-threaded program?

[jwu]

Hi, I have this strange question while doing some multi-threaded programming.

The code below output :

thread start
Destroy A=HASH(0x10124254)
thread start
Destroy A=HASH(0x101254f4)
Destroy A=HASH(0x1002f054)

with two more DESTROY calls, how can I avoid them? I am using ActiveState 5.8.4 810 on Win XP

Also, if I use  my $a : shared = A->new() then there will be another two more DESTROY calls.

use threads;
use threads::shared;
{
    package A;
    use threads;
    use threads::shared;
    sub new {
        my $class = shift;
        my $self = &share({});
        return bless $self, $class;
    }
    sub get_s {
    }
    sub DESTROY {
        print "Destroy $_[0]\n";
    }
}

my $a  = &share(A->new());
for (1..2) {
    async {
        print "thread start\n";
        $a->get_s();
    }->join();
}

Thanks.