This works out the same for package main, but it just doesn't DWIM for other packages. The first three times I read through the documentation, I assumed it was just refering to this similarity: clearly, the writers of the Perl parser could tell what package they were in, so they could expand $::foo appropriately. After all, they need to figure out packages for function calls. Instead, it means the same as $main::foo, something that a simple regexp could do for me, if I wanted it to.

Since I thought the point of the package notation was to let the globals stand out with the double colon sigil syntax, I was disappointed to learn that I'd have to hard-code the package name in multiple places: first, in the the package, and second, for all the global variables within that package.

"our" variables solve the hard-coded package name issue, but don't have a special sigil to make them stand out as globals anymore...*sigh*
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Ytrew