Depends on how good a C programmer you are. If you're reasonably good, yes. Probably a factor of two to four if the transforms are simple. More, possibly, depending on the IO subsystem. (It doesn't matter if your C program could
run 50 times faster than the perl one if you've already maxed out your IO channel going twice as fast. You'll just twiddle your thumbs more)
On the other hand it may take 5-10 times as long to write and debug the program, and maintenance/debugging it'll be a major pain relative to perl.