In this case it's probably much easier to convert to grid, rather than, pack, since you're already in effect faking your own grid layout.

  for (@data) {
    $chkReport[$i] = $frame
        ->Checkbutton()
        ->grid( -column => 0, -row => $i ); #==
    $lblReport[$i] = $frame
        ->Label( -text => $_ )
        ->grid( -column => 1, -row => $i ); #==
    $i++;
  }
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