1. first - DESTROY should still get called even if only once.
2. second sub { $bob } does not get DESTROYed either and it certainly not immutable.

package Foo;
sub print { print "@_\n"; }
sub DESTROY {
   print "@_ DESTROY\n";
}
our $bob = "x\n";
my $x = bless(sub {$bob}, 'Foo');
$x->print('$bob');
print $x->();
$bob = "y\n";
print $x->();
$bob = undef;
__END__
Foo=CODE(0xe8a278) $bob
x
y
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