$VAR1 = {
          'group2' => {
                        'strain5' => 1,
                        'strain3' => 1,
                        'strain4' => 1
                      },
          'group1' => {
                        'strain2' => 1,
                        'strain4' => 1,
                        'strain1' => 1
                      },
          'group3' => {
                        'strain7' => 1,
                        'strain6' => 1
                      }
        };
$VAR1 = [
          [
            'strain7',
            'group3',
            'strain6'
          ],
          [
            'strain3',
            'group2',
            'strain5',
            'strain4',
            'group1',
            'strain1',
            'strain2'
          ]
        ];