Add prefix and suffix hyperparameters, which would add the same prefix and/or suffix given as a character vector to all columns selected with affect_columns. Default would be character().

Maybe also allow more complex renaming schemes by passing a function to a new hyperparameter which accepts a character vector and returns a character vector of the same length. The user could then pass something like function(cols) sub("x", "y", cols). Alternatively we could implement this internally and expose pattern and replacement to the user.