my $BC = CPU::Emulator::Z80::Register16->new(
  get => sub {
    return 256 * $self->register('B')->get() +
                 $self->register('C')->get()
  },
  set => sub {
    my $value = shift;
    $self->register('B')->set($value >>8);
    $self->register('C')->set($value & 0xFF);
  }
);