Agreed. It's another case of premature optimization. If you claim to need the speed while you are still choosing the language, then either you're ignoring the real issues, or you're good enough that this conversation is pointless. :P

However, certain long lived, heavy duty server type programs certainly are much better off in a language like C. the OS, system libraries, servers like bind and apache... These systems certainly do benefit greatly from being programmed in C.

Otherwise, rapid development in perl can save a lot of time and headaches (if the syntax doesn't kill ya :P ) and then a bit of memory profiling can show you the areas that get run the most and either need to be tightened up or programmed in a lower level language.