I'd rather see novoid be an attribute of it's own, rather then an argument to another. It makes sense to use on it's own, it's not logicly a subtype of another contextual thingy.

I'd also rather it be a warning then fatal. warings::warnif("void", "Useless use of $fullydecoratedname in void context"); That'd have parity with what the core does for some builtins. For that matter, you may want to have a :NoScalar and :NoList. (:NoScalar would match sort, see perldiag's "Useless use of sort in scalar context", which I've never actualy seen. I know of no analog for :NoList, but it would seem to be required for parity.) :NoVoid should also skip running of the actual sub.