Always start by showing us the output you are aiming for:
(without that it's harder than you would guess to interpret the context and the actual problem that you are trying to solve – see XY problem - Wikipedia, and harder than it need be to actually offer you a solution)
Are you, for example, trying to produce a second list, derived from:
"hello,123,234,234,234"
and with the same calculation applied to each comma-separated segment that is numeric ?
e.g. assuming that the calculation were (* 7), an output like:
"hello,861,1638,1638,1638"
?
Or perhaps:
- applying a different calculation to each column ?
- extending this pattern over several CSV lines ?