my %macs = (
  '00:11:22:33:44:55' => {
    'response_status' => 12,
    'response_date'   => 'yesterday',
  },
  'AA:BB:66:12:13:14' => {
    'response_status' => 0,
    'response_date'   => '2004-12-31',
  },
  # ... and so on
);