RegEx to match acronyms

Question

I am trying to write a regular expression that will match values such as U.S., D.C., U.S.A., etc.

Here is what I have so far -

Answer 1

Try (?:[a-zA-Z]\.){2,}

?: (non-capturing group) is there because you want to omit capturing the last iteration of the repeated group.

For example, without ?:, 'U.S.A.' will yield a group match 'A.', which you are not interested about.