I have a spec:

(s/def ::statement (s/cat ::header ::header
                          ::delimiter ::delimiter
                          ::txs-header ::txs-header
                          ::txs ::txs))

::header, ::delimiter etc are declared using s/cat themselves, so I suppose s/tuple can't be used here.

Maybe there is a simpler way to spec this data format? The input is a CSV file parsed into a vector of vectors. Header is a number of lines, more-or-less fixed, but some are optional and may be omitted. Delimiter is a single fixed line. Txs headers is another set of more-or-less fixed lines, and txs is the rest of the document.

s/tuple might be better

For vector of fixed position fields

Too bad they are mostly, but not completely, fixed. Banks are, well, banks.

I would turn the vec of vecs into a vec of maps, then spec with s/keys

Parsing individual lines is not so bad — they can be handled by s/tuple. Parsing the sequence of lines is worse.

I'll leave it with s/cat for now.