There was a typo in the regex and nine-digit zip codes (90210-4567) weren't being properly matched.

Thanks. I added that number to the unit tests, though I didn't actually fail without your modifcation. Still, the fix makes sense.

The error was extra digits in front, e.g., 123456-7890, matching 23456-7890 instead of failing. Extra digits now fail, which is good.

Something like that: http://rubular.com/r/qDE6GNsXb4

Thanks, I extended the unit test for that: b51e86f