svoid test_replaceDollarVars() {
  assertEqualsVerbose("Hello Chris Guy $what",
    replaceDollarVars("Hello $firstName $lastName $what", firstName := "Chris", $lastName := "Guy"));
  assertEqualsVerbose("Hello Stefan, what's up",
    replaceDollarVars_dyn("Hello $userName, what's up", var
      -> eq(var, "userName") ? "Stefan" : null));
}