Not exactly, because the first warning won't show up if I happen to reference $a::z twice.

The "use of uninitialized value" message is nice, but it's not telling me that $a::z was the cause of the problem.

Basically I want to catch when the programmer mis-spelled a variable name, i.e. typed $a::z when they meant $a::x.

The names in package a will be special in that they will only be defined within package a's lexical scope.