code: function toRegex(prefix) {
    var key = appendPrefix(prefix, '(\\d+)');
    if (cache.hasOwnProperty(key)) {
      return cache[key];
    }
    var regex = new RegExp(createRegexString(key), 'g');
    cache[key] = regex;
    return regex;
  }
docs: Create a regular expression based on the given `prefix`.
  @param  {String} `prefix`
  @return {RegExp}