It is that simple! It has practical benefits. For example, if you can call that code from somewhere specific in your program, which is handy for debugging. If your `eval` function takes a lexical environment, you can also implement a debugger easily.

To test whether your logic is working properly, make your repl print out a different character when it prompts for input. For example, the toplevel repl can print out "> " whereas the inner repl prints out "repl> "

For bonus points, your repl should exit if you type Ctrl-D. That way you can go from the inner repl to the outer repl, and from there it should exit your program.