I have a flat result set from a database, joining across three tables, for the sake of this example, call them magazines, issues and articles. Each magazine has a name, each issue a number and each article a name. The result set comes back something like: 
$result = [ 
  { mag_name => "mag1", issue_num => "01", article => "art1" },
  { mag_name => "mag1", issue_num => "01", article=> "art2" },
  { mag_name => "mag1", issue_num => "02", article=> "art1" },
  { mag_name => "mag1", issue_num => "02", article=> "art2" },
  { mag_name => "mag3", issue_num => "01", article=> "art1" }
] ;

[download]
Straightforward stuff so far. Now, that structure needs to be mangled into something totally different for the benefit of HTML::Template whilst maintaining the order of things: 
$data = [
  {
     'magazine_name' => 'mag1',
     'issue_loop' => [
       {
         issue_number => '01',
         article_loop => [
            { article_name => 'art1' }
            { article_name => 'art2' }
            ],
       },
       {
         issue_number => '02',
         article_loop => [
           { article_name => 'art1' }
           { article_name => 'art2' }
           ]
        },
        {
         'mag_name' => 'mag2',
         'issue_loop' => [
            {
            issue_number => '01',
            article_loop => [
              { article_name => 'art1' },
              { article_name => 'art2' }
             ]
             },
             {
               issue_number => '02',
               article_loop => [
                  { article_name => 'art1' },
                  { article_name => 'art2' }
              ]
          }
       ] ;

[download]
I've probably mislaid some parens there but hey.

So what's a nice way of transmogrifying the former into the latter whilst preserving the order of things?

TIA,

In reply to Idiomatic way of getting from database result set to HTML::Template data structure? by davehodg

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