The value *must* contain at least one number, but *may* also contain periods and hyphens.

My first reaction is: /\d/ (4 chars). This matches any string that contains at least one number. The string may also contain periods and hyphens. And any other character for that matter - your requirement doesn't say those characters are forbidden.

But I guess the hidden requirement is that it doesn't contain anything else. You can test for that with two regexes: /\d/&&!/[^-.\d]/ (16 chars). Or, if you want to do it in one regex: /^[-.]*\d[-\d.]*$/ (18 chars).

Abigail