Flash Player 5.
my_str.lastIndexOf(substring, [startIndex])
substring An integer or string specifying the string to be searched for.
startIndex An integer specifying the starting point to search for substring. This parameter is optional.
The position of the last occurrence of the specified substring, or -1.
Method; searches the string from right to left and returns the index of the last occurrence of substring found before startIndex within the calling string. If substring is not found, the method returns -1.