Common Lisp Hello World!

Suppose a function foo writes to standard output:
(defun foo () (format t "Hello, world")) 
To capture its output in a character string, *standard-output* can be bound to a string stream and called:
(with-output-to-string (*standard-output*) (foo))

Clojure Hello World!

(println "Hello, world!")

Clean Hello World!

module hello Start :: {#Char} Start = "Hello, world!"

Hello World Caml!

print_endline "Hello world!";;