Thanks for that. Unfortunately the documentation neglects to even link to API documentation for the objects that get passed to the gcli functions or even mention their types, so I guess I'm supposed to use some sort of console with print debugging to figure out what I can do with them... too bad it seems Firefox' built-in browser console just shows up blank.
https://developer.mozilla.org/en-US/docs/Tools/GCLI/Writing_...
I added a command to toggle a preference in about:config that I switch often. It is kind of a pain to write and debug commands for the GCLI though (compared to writing javascript mapping in Pentadactyl).