my $cleaning_up;
sub DESTROY {
    print "DESTROY @{$_[0]}\n";
    my $id = $_[0][0];
    @{$_[0]} = ();
    print "CLEAN $id\n";
    return if $cleaning_up++;
    exit(14);
}
my $a = bless [1];
my $b = bless [2, $a];
my $c = bless [3, $b];