While all of the comments made here are “of course, quite valid,” it’s difficult to make categorical statements about things like this. What I generally recommend and try to do is to put all “truly-global things” into a package, ordinarily named (say ...) AppGlobals, which contains not only the storage for the global values in question, but “aggressive accessors” for them. (For instance, a subroutine that is supposed to return a database-handle, finding instead for whatever reason that the handle is undef, will die on the spot.) If we have to deal with things like “multiple blogs” or what-have-you, the logic in this one place is responsible for dealing with it appropriately.
I specifically prefer not to “pass” such things around, because an error could be introduced by any one (or more) of those “hands” that are supposed to at all times be correctly “holding it” and “passing around the right thing.” Too many potential points-of-failure for my taste. So, instead, I define one global place to put things, and I make accessors which are both smart and suspicious. Clients to this package never access the (private ...) variables directly. This discipline seems to work out pretty good . . .