use Variant1::RootClass;

package Variant1::DerivedClass;
our @ISA = qw( Variant1::RootClass );
our $VERSION = 1.00;

use strict;
use warnings;

{
    # Encapsulated class data

    my %_attr_data = #        DEFAULT          ACCESSIBILITY
        ( '_derived_entry1' => [ undef     ,        'read'],
          '_derived_entry2' => [ undef     ,        'read'],
          '_derived_entry3' => [ undef     ,        'read/write']);

    # Class methods to operate on encapsulated class data
    

    # Is a specified object attribute accessible in a given mode
    sub _accessible
    {
        my ($self, $attr, $mode) = @_;
        return $_attr_data{$attr}[1] =~ /$mode/ if exists $_attr_data{$attr};
        return $self->SUPER::_accessible($attr,$mode);
    }

    # Classwide default value for a specified object attribute
    sub _default_for
    {
        my ($self, $attr) = @_;
        return $_attr_data{$attr}[0] if exists $_attr_data{$attr};
        return $self->SUPER::_default_for($attr);
    }

    # List of names of all specified object attributes
    sub _standard_keys
    {
        my ($self) = @_;
        (keys %_attr_data, $self->SUPER::_standard_keys());
    }  
}

1;