sub do_bond {
   get LOCATION;
   check LOCATION or return;
   foreach @acc
      check PARENT_ID or { set error; next; }
      update & insert or { set error; next; }
   foreach @built
      check PARENT_ID or { set error; next; }
      update & insert or { set error; next; }
   return 1; # if you got here, everything's fine
}