!7

p {
  S s1 = "a", s2 = lower("A");
  assertNotIdentical(s1, s2); // Now more clearly showing the improvement
  S a = internPerProgram(s1);
  S a2 = internPerProgram(s2);
  assertEquals("a", str(a));
  assertEquals("a", str(a2));
  assertIdentical(a, a2);
  S b = internPerProgram("b");
  assertEquals("b", str(b));
  print("OK");
}