Extending Phone Number Validation To Add Extension

 I am not so great when it comes to understanding regex so I figured asking for a little help would be faster than googling the heck out of it.
^([\(]{1}[0-9]{3}[\)]{1}[\.| |\-]{0,1}|^[0-9]{3}[\.|\-| ]?)?[0-9]{3}(\.|\-| )?[0-9]{4}$
is what I have and it has been sufficient.  But now, I need to allow data like this:
(800)233-7164  (431143)
(800)794-4462  (2261)
What do I need here?

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