static LS ai_addDollarSignToCertainTokens(LS tok, final Set<S> set) {
  ret map(tok, func(S t) -> S { contains(set, t) ? "$" + t : t });
}

// modifies & denaturalizes the tokens (breaks connection with full text)
ifclass TokenAndRange
static L<TokenAndRange> ai_addDollarSignToCertainTokens(L<TokenAndRange> tokens, final Set<S> set) {
  for (TokenAndRange t : tokens)
    if (contains(set, t.token))
        t.token = "$" + t.token;
  ret tokens;
}
endif