split-sequence-if (predicate sequence &key start end from-end count remove-empty-subseqs key)
Returns a proper list list and an index into the sequence.
Return a list of subsequences in sequence delimited by items satisfying predicate.
If :remove-empty-subseqs is nil, empty subsequences will be included in the result; otherwise they will be discarded. All other keywords work analogously to those for substitute-if. In particular, the behaviour of :from-end is possibly different from other versions of this function; :from-end values of nil and t are equivalent unless :count is supplied. The second return value is an index suitable as an argument to subseq into the sequence indicating where processing stopped.