How exactly would you go about benchmarking this? It's my understanding that due to a bunch of perl specific features, you can't easily embed perl's regex engine alone in a C program( you could of course embed an entire perl interpreter). And obviously it wouldn't make much sense to embed pcre in a perl program. So I can't think of a way to do an apples to apples comparison.
You could time a series of perl and c programs that run a variety of regexes over various types of input, for a least common denominator feature set. But for most programs there are a number of other factors that will impact performance more than the choice of regex engine (interpreted vs compiled, i/o libraries, memory management, GC, etc)
But beyond writing programs that only do regex matching, I think the choice between pcre and perl is whether you want to write the rest of the program in C/C++ or in Perl.