sS ai_performJavaCheck_safe(S s) {
  new Matches m;
  if (!swic_trim(s, "java check:", m)) null;
  S code = $1;
  if (!isSafeCodeFragment(code))
    ret null with print("Skipping unsafe code: " + code);
  O result = javaEvalOrInterpret(code);
  if (isTrue(result)) ret "Yes";
  if (isFalse(result)) ret "No";
  ret "Not sure";
}