I was kind of hoping there would be a nice series expression that just "was regex", but I didn't find it yet.
(require :series)
(series::install)
(let ((to-filter (scan '(a b c d e)))
(filters (series '(b d))))
(collect
(choose
(#Mmember to-filter filters)
to-filter)))
(series::install :remove t)
There are only five candidate decades for someone to have written it in, I'll find it eventually..