When I was rebuilding my crosshatch plugin for the GIMP as Script-Fu Scheme a week or two ago, I ran into a beautiful little problem. It seemed that sometimes I needed to take the car (the "head of list") of the result of some Script-Fu functions for no apparent reason. In fact, the more I poked at it, the more I couldn't figure out when I didn't need to…</p>
After messing and messing with it, I finally found a paragraph buried in Section 3.5 of the tutorial documentation that helped me out. You can see the relevant excerpt here. I've also marked it up a bit to try to help the GIMP folks out here.
Several hours. (B)