I handle multiline input by checking to see if the parser runs into EOF and building up the code in the REPL until it successfully parses, then do a couple more checks. I'm not sure how elegant this is in the long run and it makes for a bit of a couple weird edge cases -- for instance, expressions need to return successfully on EOF so the REPL can properly evaluate them. I'm not sure if this is a problem for you (allowing arbitrary expression evaluation without making it a statement) but I figured it might be worth noting 👍