Transforming Field Value with Rex/Regex?

Hey! So I have this field: "user1 user2 user3 user4 user5 user6 (.....)" and I wanted it to look like "(account="user1" OR account="user2" OR account="user3" OR (.....))" without using format or append/join, but using regex/rex. Any ideas on this? PS1: the value isn't actually user*, it is a combination of letters and numbers, like uiw849tghuADIIJO34ow. Thanks in advance!!