Consider getting a stream of data and that we store it through consing,
this has the drawback that the list will grow indefinitely. What you want
is to make sure  that any data that you need for computation a pointer to
the start and end of the data would mean that by modding the mark procedure
will tell the special cons cell that a part has a start reference or an end
referense. Then in a custom sweep procedure you would be able to tell if
these markings increments/decrements counters when you can discard data for
gc. You would not need any magic at all but custom mark procedures and a
custom sweep procedure. I find this tool pretty interesting.

Maybe a little project that implements this would be cool to have WDYT?

Cheers!