What I have: 123456789-987654321
What I need: 3456789-4321
(keep last 7 digits from 1st group and keep last 4 digits from 2nd group)
(\d{7})- gets me 3456789-
((\d{4})$(?<=)) gets me 4321
I can't figure out how to combine the 2 to get what I need.