static S formatXYZ(S pattern, L<S> args) {
  ret join(formatXYZ(javaTok(pattern), args));
}

// modifies tok!
static L<S> formatXYZ(L<S> tok, L<S> args) {
  for (int i = 1; i < l(tok); i += 2) {
    S t = tok.get(i);
    int idx = formatXYZ_varToIndex(t)-1;
    if (idx >= 0 && l(args) > idx)
      tok.set(i, args.get(idx));
  }
  ret tok;
}

static S formatXYZ(S pattern, S... args) {
  ret formatXYZ(pattern, asList(args));
}