This has always struck me as significant effort invested in making a bad user experience only slight less bad: the REPL overloads the meaning of "enter" to mean

This has always struck me as significant effort invested in making a bad user experience only slight less bad: the REPL overloads the meaning of "enter" to mean both "insert a new line" and "execute command", and then attempts to guess what the user meant by tweaking the grammar of the language. Why not distinguish between "insert a new line" and "execute command" as two distinct inputs, and eliminate all ambiguity ?