Thanks for the responses.
Actual validation was never an issue here.
The original question related to something I have had to use for the best part of my career (ever tried to register a domain with Nominet with user-provided data ??) ... and overly relying on the Laziness aspect of the perfect programmer, I tend to opt for the cut and paste method a bit to often.

Roy Johnsons response I found very legible , and of course pasting one line is a tad quicker than three ;)

cheers