How do you declare a function that doesn't return anything? For instance, a
C++ swap function might be declared
template <class X>
void swap(X &x, X &y);
It would be nice to declare the corresponding Perl6 function as
sub swap ($x is rw, $y is rw) returns nothing {...}
or something similar.
This would be an absolute necessity if you wanted to emulate C++, Java, or
any other strongly typed language.
Also, it could be useful for causing a compile-time error if someone types
something like
$z = swap($x, $y);
Joe Gottman
