Canon states the following about PIC. As people have said it does not affect RAW, but if it did then would it be keeping with the concept of RAW. Not really, since RAW essentially the image as seen by the sensor. I do shoot RAW, with a mix of Canon and Sigma lenses and have to say that doing the correction for the Canon lenses with a clickmor two is a convenience. To say you won't use PIC because you shoot RAW seems at odds with the fact that virtually all our final output is JPG or a similar format.
The Peripheral Illumination Correction function has no effect on image data when the cameras are set for RAW, sRAW1 or sRAW2 recording modes, but the P.I.C. algorithm can be applied to these images during post-processing in compatible versions of DPP, together with additional image improvements including chromatic aberration correction and distortion control.