Regexp for an IPv4 address with a prefix (CIDR notation)

New regexp for future use - an IPv4 address with a prefix (CIDR notation)

^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])(?:\/([0-9]|[1-2][0-9]|3[0-2]))?$