package Foo;

use BaseClass;
our @ISA = qw(BaseClass);

Foo->define_attributes(
    name   => 'STRING',
    age    => 'NUM',
    weight => 'NUM',
);

sub initialize {
    my $self = shift;

    $self->SUPER::initialize(@_);
    my ($name, $age) = $self->get('name', 'age');
    print "My name is $name and I am $age years old!\n";
    return 1;
}

1;
_____

package Bar;

use Foo;

my $person = Foo->new(name => 'Child1', age => 5);
$person->set(weight => 40);