And creating a DSL for your problem, and user functions being identical to build in functions, and being able to fully extend the language yourself, to the poin

And creating a DSL for your problem, and user functions being identical to build in functions, and being able to fully extend the language yourself, to the point of adding custom conditionals or whatever, and several other things.... Aside from the functional vs concatenative paradigms, they share a lot of development philosophy, and give a lot of the same superpowers to the developers.