I haven't gotten it reliably working either way, can you give a working example?

Well, it depends rather on what exactly you are referring to as it, but

use threads;
use threads::shared;

sub X::DESTROY { warn "X::DESTROY(@_)\n" }

my $x = bless [], 'X';
share $x;
$x->[0] = 1;

sub f {
    $x->[0]++;
    warn "x->[0] = $x->[0]\n";
}
threads->new(\&f)->join for 1..5;

__END__
$ perl587t /tmp/p
x->[0] = 2
X::DESTROY(X=ARRAY(0x9d8b218))
x->[0] = 3
X::DESTROY(X=ARRAY(0x9da0500))
x->[0] = 4
X::DESTROY(X=ARRAY(0x9da0500))
x->[0] = 5
X::DESTROY(X=ARRAY(0x9da0500))
x->[0] = 6
X::DESTROY(X=ARRAY(0x9da0500))
X::DESTROY(X=ARRAY(0x9cd3c30))
[download]

Dave.