No, I am afraid I spoke too soon. This does not work at all. Your code produces the following:

$VAR1 = [
  {
    'level' => 0,
    'name' => 'root',
    'children' => [
      {
        'level' => 1,
        'name' => 'one',
        'children' => [
          {
            'level' => 2,
            'name' => 'bar'
          },
          {
            'level' => 2,
            'name' => 'baz',
            'children' => [
              {
                'level' => 3,
                'name' => 'two'
              },
              {
                'level' => 3,
                'name' => 'three'
              },
              {
                'level' => 3,
                'name' => 'four'
              }
            ]
          }
        ]
      },
      {
        'level' => 1,
        'name' => 'five'
      }
    ]
  },
  $VAR1->[0]{'children'}[1]
];
[download]

'one' does not have any children.

Sorry, but this won't work for me either. Maybe this is a harder problem than I thought it would be.