In order to filter arrays one could define a macro filter, which
takes an array and an expression, and evaluates the expression once
for each element in the array. Something like this:
filter(.path.to.array, number(.price) > 20)
This can't be a function, because the second argument has to be evaluated many times, but it's perfectly doable as a macro.
Alternatives are FOR (...) ... IF (...) for-filter
and predicates.