until (eof FILE) {
  for my $count (3, 2) {
    my @set = map scalar <FILE>, 1 .. $count;
    my ($time, @totals);

    for (@set) {
      chomp;
      my @f = split /\t/;
      $time ||= shift @f;  # only want the FIRST time
      $totals[$_] += $f[$_] for 0 .. $#f;
    }

    print OUT join("\t", $time, map $_/$count, @totals), "\n";
  }
}