my %default = %default_values;  # shallow copy
    $default{ AUTHOR } =
       +{ %{ $default_values{ AUTHOR } } };  # copy next level

    my $self = ref($class) ? bless( \%default, ref($class) )
                           : bless( \%default, $class );


##</code><code>##

my $self = bless deep_copy( \%default_values ), $class;