I first heard about L-Systems a number of years ago in the context of an elective masters course on computer graphics, where we briefly touched on approaches for procedural geometry generation.

The way it was introduced to us, was to basically apply a parsing grammar backwards, IIRC using an iterative match-and-generate approach, to produce a command stream for a renderer.

I remember finding the idea of using a parsing grammar in this way quite interesting and wondered about other areas where this could be used. For some reason, programmable shell-completion came to my mind, i.e. encode a command line options for a program using a recursive grammar with "expand a file path here" or "call an external helper (e.g. git)" as terminal symbols. Throw in capture groups for terminals and this kills most use cases where the imperative approach in Bash gets very tedious.

I keep recalling that idea from the back of my mind every time I see L-Systems featured on HN. I guess/hope most newer shells learnt from Bash and already do something like this, but I honestly was just too lazy to investigate this any further (so far).