Thanks ikegami! Unfortunately the database I'm dealing with doesn't quite let me simplify down to just parent-child IDs. The join I mentioned above is between about 10 tables, all with distinct sets of IDs, so the result of the join, as retrieved by selectall_arrayref looks like:

my $data = [
   [ 'parent1', 'child1a', 'child2a', undef,    ],
   [ 'parent1', 'child1b', 'child2b', 'child3b',],
   [ 'parent1', 'child1c', undef, undef,],
];

[download]

While playing with your solution, I got really close to what I need:

my @results;
foreach my $row (@$data) {
   push @results, treeify(@$row);
}

print Dumper @results;

sub treeify {
   my @list = @_;
   my $node = shift @list;
   return {} unless $node;
   return {$node => treeify(@list)};
}

[download]

Which yields:

$VAR1 = {
          'parent1' => {
                         'child1a' => {
                                        'child2a' => {}
                                      }
                       }
        };
$VAR2 = {
          'parent1' => {
                         'child1b' => {
                                        'child2b' => {
                                                       'child3b' => {}
                                                     }
                                      }
                       }
        };
$VAR3 = {
          'parent1' => {
                         'child1c' => {}
                       }
        };

[download]

Which sort of brings me back to my original query, figuring out how to merge those three hashes.

Any thoughts?

In reply to Re^2: Generating a Hash of Hashes Recursively to Display Database Hierarchy by c4onastick
in thread Generating a Hash of Hashes Recursively to Display Database Hierarchy by c4onastick

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