Yes, even core modules. This Linux box in front of me has 18 top-level core modules while a "better" install has 64 of those. And I actually added a few of those 18 "by hand", which was trickier than some might expect and I abandoned adding some others because it was just too much work. And I've seen more than one Perl installation that had even fewer than that.

And I got DBI/DBD working on the above Linux box after working around some of many authors' rash assumptions about what modules are always going to be available. Many of those work-arounds were trivial to code (the amount of functionality they were depending on from the module was trivial -- and yet they just die if it isn't there) but finding them all was a big pain.

Yes, I realize I'm unusual in even acknowledging that such sub-core installations of Perl exist in the world, much less in doing a tiny bit of extra coding in some cases to work around missing modules when it is easy.