closures, upvalues good repl arrays, hashes, other useful types arrays: get index set index get length literals append concat conformation of at least arithmetic over arrays hashes: get index set index get count literals merge? delete? should probably implement ht with keys other than strings user-defined structs, somehow, maybe good loops numeric for array for each functional variants of the above variants of the above that record an array of all their results declarations inline pattern matching probably doesn't need to be too complex garbage collector go thru everything make sure references are kept around properly macros error handling record line and col of everything not sure how to do error handling in language but at least make the error messages good more sophisticated testing of errors instead of just literally matching error message tidy and clean the code properly do bounds checking everywhere etc