You can't do anything more easily in C as opposed to Perl. That has never been a question.Really? Written any high-performance gigabit ethernet drivers in perl lately? (Or, for that matter, written perl in perl lately?)
It's not even a matter of possible. It's a matter of ease. It's easier to write device drivers in C than perl, and it's easier to write interpreters in C than perl--if it wasn't parrot and more of perl 5 would be written in perl. They aren't, because it isn't easier.
Ease is task-dependent. You're dismissing whole realms of problems without good cause, apparently out of a dislike of C. I loathe C some days, but it's still a better language (including ease of use) for some problems than perl is, or ever will be.