I personally am very interested in IPv6, but the regular expression notation is more complex than IPv4: IPv4 has four decimals separated by dots; IPv6 has as many as 8 double-byte hex characters, sometimes as few as one (e.g. ::1). Plus, other than myself, I know few people who regularly use IPv6. It&#x27;s not an intractable problem; I just wasn&#x27;t ready to put the effort into it.