I have sx 10 is firmware 101b chdk 0.9.9-885.
When I have .RAW or .DNG without corresponding .jpg in a folder and when I select purge raw on the folder (e.g. 119CANON or DCIM) the confirmation question is displayed, but after selecting YES nothing happens.
.DNG or .RAW - .JPG pair is deleted after camera restart but without restart only .jpg is deleted and orphaned .DNG or .RAW remains.