Calling void functions

I'm informed that the last statement of a function that returns void cannot be 
a SELECT.  How else is one supposed to call another function which also 
returns void?

E.g.,

CREATE FUNCTION foo (a int, b int) RETURNS voidLANGUAGE plpgsqlAS $$ do important things $$;

CREATE FUNCTION foo (a int) RETURNS voidLANGUAGE sqlAS $$ SELECT foo($1, default-value); $$;

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/