Ok, here is my noob question of the month. The docs on expansions state, and I verified, that:
when turned into environment variables, list-type options, $kak_reg_x, and “quoted list” values will be shell-quoted so the shell doesn’t get confused about how many items the list contains. You will need to apply eval to get back the original values.
So we’ll need to apply ‘eval’ to what may be uncontrolled user input. Is there nothing here to worry about? What if the register contains nasty things (e.g.,: ‘33; rm myfile.txt’)?