code: function stripBraces(state, str) {
    if (!str.match(TEMPLATE_REGION)) {
      handleError(state, 'Expected ' + str + ' to match ${...}');
      return str;
    }
    return str.slice(2, -1);
  }
docs: Warn of string does not begin '${' and end '}'
  @param str the string to check.
  @return The string stripped of ${ and }, or untouched if it does not match