|No such thing as a small change|
The simple fact is that not only do you not have to declare global variables -- "fully qualified variable names" are always globals --, you cannot declare them. Perl has no mechanism for doing that.
You seem to be equating the action of our with that of my, but they are in not equivalent. my actually creates new variables, but our simply allows you silent, unqualified access to them in the current lexical scope.
One possibility that might in some way meet your requirement would be to use Hash::Util::lock_keys() to restrict the package hash to just those keys you require.
Update: A little explanation of the idea:
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.