When the last writer on a fifo closes its end, the reader will see end of file. Since you are opening and closing the fifo for each line, the reader is only getting one line before seeing EOF.

Do something like this:

use FileHandle;
...
open(FIFO, ">", "named.pipe") or die "open failed; $!";
FIFO->autoflush(1);
...
for $file (@list) {
  print FIFO $file, "\n";
  sleep(...);
}
close(FIFO);
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Or, have your reader program immediately re-open its end after it detects EOF.