There are simply too many unstated possibilities to give a good answer.

Will the adapted code be Perl? If not, any conclusions drawn based upon perl code are useless.

If it is perl, how will perl be built for that environment?

Will it use stdio or perlIO?

If stdio, will the C runtime library be an ANSI-C complient library?

Even the version of Perl makes a difference. In early 5.8.x builds, Perl's IO seemed to loose some of it's 5.6.x performance. In 5.8.4 and 5.8.5, much of that has been regained.

I'm not sure how reading from a stream (socket?) will affect things. Logically, if the source is not from disk, that may reduce diskhead thrash, but then, if the stream is slower than the disk, then the stream becomes the limiting factor and buffering the output will have no beneficial effect.

Finally, many realtime and realtime capable OSs have asynchronous IO capability. Some will even queue reads and writes and dynamically re-order the queues to minimise head movements. Any attempt to define best practices without fairly detailed knowledge of the underlying systems and mechanisms is not possible.