open(F, "/usr/dict/words") || warn;  # File to process
$s=-s F;
$|=1;
while(<F>) {   # Binary read() or readline()...whatever.
      # Do something with the data I presume...
      printf "\rComplete %.2f", 100*tell(F)/$s;
}

##</code><code>##

  printf("\rComplete: %.2f", 100*tell(F)/$s) unless $i++ % 10;