You might want to use a Lookup transform.

Instead of putting the logic into a case statement you can create a table with MyValue and MyOutput columns. Then run the output from your file into the lookup, join the two data sets on MyValue and return MyOutput from the reference table.

To handle the “ELSE Bah” condition (when there is no match in the reference table) you can set the lookup to ignore errors. Then add a derived column task after the lookup with something like: ISNULL(MyOutput) ? “Bah”: MyOutput.

This gives you the advantage that when you add or change MyValue conditions you don’t have to touch the code you can just insert/update a reference table.