use strict;
use warnings;

use DBI;


sub treeify {
    my ($sth) = @_;

    my %root = ( _children => [] );
    my %children;

    while (my $row = $sth->fetchrow_hashref()) {
        my ($id, $parent_id) = @$row{qw( Child Parent )};

        my $parent = ( defined($parent_id)
            ? $children{$parent_id} ||= { _children => [] }
            : \%root
        );

        my $node = $children{$id} ||= {};
        %$node = ( _children => [], %$row );

        push @{ $parent->{_children} }, $node;
    }

    return \%root;
}


{
    my $sponge = DBI->connect(
        'dbi:Sponge:', '', '',
        { RaiseError => 1 }
    );

    my $sth = $sponge->prepare(
        'SELECT * FROM Fruit',
        {
            NAME =>   [qw( Parent  Child  Desc             Property1  
+Property2        )],
            rows => [ [     undef,    50, 'Fruit',         'hidden',  
+'non-searchable'  ],
                      [        50,   100, 'Apple',         'hidden',  
+'non-searchable'  ],
                      [       100,   110, 'Granny Smith',  'Visible', 
+'searchable'      ],
            ],
        }
    );

    my $tree = treeify($sth);

    use Data::Dumper;
    print Dumper $tree;
}
[download]

Based on Generating a Hash of Hashes Recursively to Display Database Hierarchy. Should use a classes.