I have a requirement where in i need to delete old entries in a hashref. For e.g. in the below data section only "2017/06/28" key value pair should survive.
Rest all key value pairs should be deleted. Please provide me ideas how to accomplish this.

**DATA**

```
$data_hashref = {
          '2017/06/27' => {
                            'start' => '13:07:00',
                            'end' => '23:47:00'
                          },
          '2017/06/15' => {
                            'start' => '07:11:00',
                            'end' => '00:18:00'
                          },
          '2017/06/28' => {
                            'end' => '06:37:00',
                            'start' => '00:06:00'
                          },
          '2017/06/17' => {
                            'start' => '09:17:00',
                            'end' => '10:17:00'
                          }
        };

```

**RESULT**

```
$data_hashref = {
          '2017/06/28' => {
                            'end' => '06:37:00',
                            'start' => '00:06:00'
                          }
        };

```