One Regular Expression to validate US and Canada ZIP / Postal Code

Question

I am developing a stationery program. Customers have choice to pick their region either US or Canada. When they enter address they have to enter ZIP/Postal code. I am trying to

Answer 1

Furthering the answer above you could add (?i) to the beginning of the regex to make is case insensitive. So it would look like this:

^(?i)(\d{5}(-\d{4})?|[A-CEGHJ-NPRSTVXY]\d[A-CEGHJ-NPRSTV-Z] ?\d[A-CEGHJ-NPRSTV-Z]\d)$