I know when I was using a combination of Win32::Gui and Win32::Ole and I would do lots of file crunching/number crunching, opening and closing lots of excel spreadsheets and so-on it seemed like I had memory leaks and general instabilities that I never fully tracked down.
I think that this is the question that you are asking? Is there a problem having a perl script that runs indefinitely, will there be be in pitfals to doing it, memory leaks, zombie processes, etc...? For the task that you are doing my inclination is no, you should be fine, but I do not have nearly the knowledge base or experience as many of the others here. So hopefully someone else can concur, or if any, point out the potential problems.
Comment on Re: Using pipe and reading from the stdin
Yes, exactly what i mean. Is there something happening that i am unaware of?
Far as i understand, keeping tail in the "-f" mode doesn't keep the lines in the memory space nor does perl using while <STDIN> do that, so it should only be a matter of printing a line through external program and seeing if we have another line to print again.