#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{   package My::Root;
    use Scalar::Util qw{ refaddr };

    our %attr;
    sub new {
        my ($class, $name) = @_;
        my $o;
        $attr{$class}{ refaddr(\$o) }{name} = $name;
        bless \ $o, $class;
    }
    sub name {
        my ($self) = @_;
        $attr{ ref $self }{ refaddr($self) }{name}
    }
    sub count {
        my ($class) = @_;
        return scalar keys %{ $attr{$class} }
    }
}

{   package My::Child;
    use parent -norequire => 'My::Root';
}

my $o1 = 'My::Root'->new('root1');
say $o1->name;

my $children = map 'My::Child'->new("child$_"), 1 .. 10;
say "Number of Root instances: ", 'My::Root'->count;
say "Number of Child instances: ", 'My::Child'->count;