:- module hello.
 :- interface.
 :- import_module io.
 :- pred main is det.
 
 :- implementation.
 main :-
        io.write_string.

 :- module fib.
 :- interface.
 :- import_module io.
 :- pred main is det.
 
 :- implementation.
 :- import_module int.
 
 :-func fib = int.
 fib =  + fib).
 
 main :-
        io.write_string = ", !IO),
        io.write_int, !IO),
        io.nl.
        % Could instead use io.format = %d\n",, !IO).