your @arr array has never been populated with anything

It is for me. When I run the 1st code snippet (no strictures), I see something in @arr:

use Data::Dumper; print Dumper(\@arr);
$VAR1 = [
          [
            {
              'key' => 12,
              'lop' => 9,
              'pl' => 1
            },
            {
              'key' => 12
            }
          ]
        ];
[download]

What happens when you run it? The 2nd snippet has compile errors for me.