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;
}