[sargstuff]

> "... (and not just by passing opaque strings to it, but by actually expressing awk-style commands in a proper datastructure) ..."

Explicit, in language data structures are not a feature at the chomsky language level that traditional awk targeted at, but in-place file block state manipulation can be setup/arranged in a data structure form.

Something like a bnf/ebnf language data structure description would need to be used/processed by an awk script to make use of data structures within an awk script. aka ANI spec in BEGIN section. Something akin to overlaying a script on top of a script and/or printf being passed description of string format.

awk not traditionally set up to do homoiconicity forms within same script instance. (abuse of system call & gawk exentions not withstanding)