my $sth = $db->prepare("SELECT curr_parent_id FROM demstock2 WHERE ds_id=?");
my $move_sth = $db->prepare("UPDATE demstock2 SET curr_parent_id=? WHERE ds_id=?");
my $action_sth = $db->prepare("
INSERT INTO action
(action_id, action_type, ds_id, occurred,          ref_no,  staff_id) VALUES
(NULL,      'MOVE',      ?,     CURRENT_TIMESTAMP, ?, ?)");
for my $child (@built, @acc) {
  #Find out if it still is in free stock
  $sth->execute($child) or ...
  my $current_status = $sth->fetchrow_hashref;
  if($current_status->{"curr_parent_id"} != 0) {
    print ...;
    next;
  }
  $move_sth->execute($main, $child) or ...
  $action_sth->execute($child, "0,$main", $caluser) or ...;
}