Lisp interpreter in Matlab. Just because.
>> repl
matlisp> (+ 1 2)
3
matlisp> (car (list 1 2 3))
1
matlisp> (define fact
... (lambda (n)
... (if (<= n 1)
... 1
... (* n (fact (- n 1)))
... )
... )
... )
matlisp> (fact 10)
3628800
matlisp>