- commafy ["donkey", "mule", "horse", "camel", "llama"];
> val it =
    ["donkey", ", ", "mule", ", ", "horse", ", ", "camel", ", ", "llama"] :
  string list

- print (String.concat it ^ "\n");
donkey, mule, horse, camel, llama
> val it = () : unit

- commafy ["foo"];
> val it = ["foo"] : string list