rgxFindMatchPos = function (str, left, right, flags) {
  'use strict';
  var f = flags || '',
      g = f.indexOf('g') > -1,
      x = new RegExp(left + '|' + right, 'g' + f.replace(/g/g, '')),
      l = new RegExp(left, f.replace(/g/g, '')),
      pos = [],
      t, s, m, start, end;

  do {
    t = 0;
    while ((m = x.exec(str))) {
      if (l.test(m[0])) {
        if (!(t++)) {
          s = x.lastIndex;
          start = s - m[0].length;
        }
      } else if (t) {
        if (!--t) {
          end = m.index + m[0].length;
          var obj = {
            left: {start: start, end: s},
            match: {start: s, end: m.index},
            right: {start: m.index, end: end},
            wholeMatch: {start: start, end: end}
          };
          pos.push(obj);
          if (!g) {
            return pos;
          }
        }
      }
    }
  } while (t && (x.lastIndex = s));

  return pos;
}
Unescape HTML entities
@param txt
@returns {string}