How to implement minikanren 'appendo' in J/APL?

Question

I've been trying hard to implement Minikanren in J,but after making good progress up to lazy streams, conjunction, disjunction, and equivalence constraints, I am now completely stuck on the appendo relation.

Specifically, I'd like help (code, books, documents, etc.) on how to implement something like appendo with J/APL conjunctions/operators since those only allow 2 arguments (4 if yielding a value type).

core implementation

attempts at appendo

Thanks!