Umeboshi is japanese apricot pickles. I like :)
This application is something like Common Lisp REPL.
However, umeboshi is still under developing :)
$ cargo run
umeboshi>> Hello world!
Hello world!
umeboshi>> (+ 1 2)
3
umeboshi>> (eq 4 (* 2 2))
true
umeboshi>> (define x 12)
umeboshi>> (+ $x 18)
30
umeboshi>> (if (eq $x 12) Equal NotEqual)
Equal