When I have a one-time computation job that takes an hour to write and two hours to run in Perl, but in C takes 10 hours to write and half an hour to run, then Perl is faster than C.

And these one-time/rare/short jobs are much more frequent than intense, high throughput C code like the nginix web server or the node javascript interpreter.

I see your point, C is definitely the choice for long running jobs or jobs that will be run more than a handful of times, in my experience however I'm writing a lot of one-off scripts that take 30 seconds tops to run so Perl wins out pretty hard over C.