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$result = [ 
  { mag_name => "mag1", issue_num => "01", article => "art1" },
...
  { mag_name => "mag1", issue_num => "02", article=> "art2" },
  { mag_name => "mag3", issue_num => "01", article=> "art1" }
] ;

$data = [
  {
...
              ]
          }
       ] ;