private String generateUniqueVarName(Set<String> existingNames, boolean end) {
    String prefix = end ? END_PREFIX : "VAR";
    int i = 0;
    while (myVarNames.contains(prefix + i) || existingNames.contains(prefix + i)) {
      i++;
    }
    return prefix + i;
  }
private String generateUniqueVarName(Set<String> existingNames, boolean end)