sub main::changeXYZ (\@@) {
  my $arg = shift;
  my $obj = tied @$arg;
  Carp::croak(
    "First arg to main::changeXYZ must be array tied to Tie::ArrayXYZ"
  ) unless defined($obj) and $obj->isa("Tie::ArrayXYZ");
  return $obj->CHANGEXYZ(@_);
}