I fail to see how a POF (plain old filehandle) doesn't do what you want it to. Basically, you have a file, a script for processing the file, and script output that you want to redirect to another file. Why do you need pipes?

open IN, "some_file" or die $!;
open OUT, ">>some_other_file" or die $!;

#generic file processing
while (<IN>) {
     #process...
     print OUT $result;
}
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