Fellow Monasterians

In preparation for a nested HTML::Template tmpl_loop I loop through the AoH results of a MySQL query attempting to add a second AoH to a key of the original AoH. (I whittled this down as much as possible)

my $stmt = 'SELECT projects FROM time_sheet WHERE subscriber_id = ?'; 
+     
my $proj = $dbh->selectall_arrayref($stmt, {Slice => {}}, $subscriber_
+id);   

$stmt = 'SELECT users FROM time_sheet project_id = ?';
   
for my $i ( 0 .. $#$proj ) {
   my $time = $dbh->selectall_arrayref($stmt, {Slice => {}}, $project_
+id);
   
   for my $j ( 0 .. $#$time ) {
      push @users, $time->[$j];
   }

   $proj->[$i]{'users'} = \@users;
   undef @users;
}
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But a Data::Dumper produces a bizarre value for users =>

print Dumper($proj);
$VAR1 = [
          {
            'number' => 'CGL00507',
            'project_title' => 'Website',
            'subtotal' => 2,
            'users' => $VAR1->[0]{'users'},
            'project_id' => '7599'
          }
        ];
[download]

Strange, because when I run a separate test:

my $AoH_class = [ 
                  { 
                    'class' => 'Algebra',
                    'room'   => '204',
                     },
                  { 
                    'class' => 'Science',
                    'room'   => '413',
                     }                     
                  ];

my @AoH_algebra = ( 
                    {
                      'name'   => 'Fred',
                      'level'  => 'junior',
                    },
                    {
                      'name'   => 'Barney',
                      'level'  => 'senior',
                    }
                  );
$AoH_class->[1]{'students'} = \@AoH_algebra;

print Dumper($AoH_class);
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I get the desired results of:

$VAR1 = [
          {
            'class' => 'Algebra',
            'room' => '204'
          },
          {
            'students' => [
                            {
                              'level' => 'junior',
                              'name' => 'Fred'
                            },
                            {
                              'level' => 'senior',
                              'name' => 'Barney'
                            }
                          ],
            'class' => 'Science',
            'room' => '413'
          }
        ];
[download]

What am I missing, fellow monks? TIA