[{_id:"1",val:"admin"},{_id:"2",val:"employee"},{_id:"3",val:"admin"}]

db.collection.update({},[{"$set":{"val":{"$switch":{"branches":[{"case":{"$eq":["$val","admin"]},"then":"admin-en"},{"case":{"$eq":["$val","employee"]},"then":"employee-en"}],"default":"$val"}}}}],{"multi":true})