TRYFAIL(debuged_remove(head,"12a")); TRYFAIL(traverse(head));
TRYFAIL(debuged_remove(head,"12b")); TRYFAIL(traverse(head));
TRYFAIL(debuged_remove(head,"12")); TRYFAIL(traverse(head));
TRYFAIL(debuged_remove(head,"12a")); TRYFAIL(traverse(head));
TRYFAIL(debuged_remove(head,"12b")); TRYFAIL(traverse(head));
TRYFAIL(debuged_remove(head,"12")); TRYFAIL(traverse(head));