<check os here>?`clear`:`cls`;

You need a print for that one, as `clear` actually prints escape sequence, so <check os here>?print`clear`:`cls`.

Also, I think that just print`cls;clear` should work too, as on windows this gives cls a command-line argument which it probably ignores (or it obeys it and makes the console real shiny clear); on linux the clear should hide whatever error cls prints.