gistfile1.perl

package Stuffer;
use Moose;
has all_stuff => (
  isa => 'HashRef',
  traits => ['Hash'],
  handles => {
    get_stuffed => 'elements',
    _has_stuff => 'exists',
    _get_stuff => 'get',
    _set_stuff => 'set',
  },
);
sub add_stuff {
  my ($self, %new_stuff) = @_;
  for my $key (keys %new_stuff) {
    $self->_set_stuff(
      $key,
      $self->_has_stuff($key)
        ? ($self->_get_stuff($key) . $new_stuff{$key})
        : $new_stuff{$key}
    );
  }
}

use Data::Dumper;
my $s = Stuffer->new;
$s->add_stuff(x => 1);
$s->add_stuff(y => 2);
$s->add_stuff(x => 3);
print Dumper { $s->get_stuffed };