I want to build kind of a “template string” for lay people (not that much) so they can receive an input (JSON) and create an output (also JSON) via web interface. Template example:

{
   exampleArray: {{input.prices.filter(price -> price <= 100)}}
}

Any tips on how to build this kind of “template string”? Regex? Finite state transducer?

That almost looks like a small programming language 😒imple_smile:. I'd tokenize it, actually parse it with recursive descent and then walk the tree to run it.