I'd treat this bit of code as a black box. In other words, the comment should say what input is expected and what will come out again. The "how" part is left as an exercise to your future self :)
Reasoning : you can't be sure that your comment will make things any more understandable at some point in the future, but with "black box code", you can at least be sure your future self will know how to rewrite that bit, should you feel the need to.
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
Note: All code is untested, unless otherwise stated