Dang, I was getting too complicated there, with the alarms and opening and closing the pipe ... simplifying per your suggestion has fixed the issue under Ubuntu, and it still works fine under Rocky

  # Open pipe
  OPENPIPE:
  unless (open $fifo, '<', $pipe) {
    log_it("Cannot open $pipe: $!");
    sleep 5;
    next OPENPIPE;
  }

  READPIPE:
  while (my $line = <$fifo>) {

    next READPIPE unless defined $line;
    chomp $line;

    # Process line
    next READPIPE unless $clean = strip_junk($line);
    next READPIPE unless $log   = find_log_name($clean);
    ($text) = ($clean) =~ /^\w+\s+(.*)/;
    write_line($text);
  }
[download]

Thank you, --sk