One way to do it is to eliminate all of your problem characters first. This way, you won't have to think through a more complex RE:
s/\D//g;
/(\d{10})(\d*)/;
Of course, this assumes that all phone numbers have the correct numbers in all the right places (three digit area code, seven digit number, and possibly an extension). It'll probably be right for a good number of rows, but the only way to be sure is to eyeball the output and compare it.
Hope this helps!
--
jwest
-><- -><- -><- -><- -><-
All things are Perfect
To every last Flaw
And bound in accord
With Eris's Law
- HBT; The Book of Advice, 1:7