Probably not the most efficient way to use Tie::File, but I have a subroutine that I use to tie @arrays to files and push or shift the information from the @arrays.
Different threads are working at the same time, and I am sure I can do a better job of working with the Tie::File. I am glad you said Tie::File is probably not leaky. I use it on other projects and don't have a problem with it, but those projects are not multithreaded.
In the next few days, I will test something and post what I use for the test. I wrote a very simple script (2 threads) that uses my method for utilizing Tie::File and the script kept growing by 4KB at a time. After I post, I am hoping someone can point out my flaw.

Thanks!