code: function(str, flags) {
          flags = flags || '';
          Y.DOM._regexCache = Y.DOM._regexCache || {};
          if (!Y.DOM._regexCache[str + flags]) {
              Y.DOM._regexCache[str + flags] = new RegExp(str, flags);
          }
          return Y.DOM._regexCache[str + flags];
      }
docs: TODO: move to Lang? 
  Memoizes dynamic regular expressions to boost runtime performance.
  @method _getRegExp
  @private
  @param {String} str The string to convert to a regular expression.
  @param {String} flags optional An optinal string of flags.
  @return {RegExp} An instance of RegExp