open LINETO, ">./lineto.txt";
$oldfh = select(LINETO); $| = 1; select($oldfh);

for ($1 etc. etc.) {
  #do you stuff here
  ##done with stage $i?
  seek LINETO,0,0;
  print LINETO "$i\n";
  #post cleanup.
}
print LINETO, "Finito\n";
close LINETO;