ok 1 - +, tied hash
ok 2 - +=, normal hash
# Operation "=": no method found, argument in overloaded package Test at /tmp/p line 52.
...

##</code><code>##

   '=' => sub { bless [ @{$_[0]} ], 'Test' },

##</code><code>##

use overload
    '+'  => \&append,
    '+=' => \&append,
    '='  => => sub { bless [ @{$_[0]} ], 'Test' };