use Foo::Bar;
my $fb = Foo::Bar->new;
$fb->[0] = 12; # here Foo::Bar::STORE($self,$index,$value) is called
print $fb; # not sure, maybe Foo::Bar=SCALAR(0x1835bfc)?

##</code><code>##

use Foo::Bar;
tie my @array, 'Foo::Bar';
$array[0] = 12; # here Foo::Bar::STORE($self,$index,$value) is called