foreign_t
pl_hello(term_t to)
{ char *s;

  if ( PL_get_atom_chars(to, &s) )
  { Sprintf("Hello \"%s\"\n", s);

    PL_succeed;
  } else
  { term_t except = PL_new_term_ref();

    PL_unify_term(except,
                  PL_FUNCTOR_CHARS, "type_error", 2,
                    PL_CHARS, "atom",
                    PL_TERM, to);

    return PL_raise_exception(except);
  }
}