open(IN, $oneper) or die "Can't open file $oneper for reading: $!\n";
open(INDEX, ">:raw","$file.idx") or die "Can't open $file.idx for read/write: $!\n";

syswrite INDEX, pack('N',0),4;
while (<IN>) {
syswrite INDEX, pack('N', tell INDEX), 4;
}
close INDEX;

##</code><code>##

open INDEX, "<:raw","$index" or die "Can't open $index for reading: $!";
my $len = -s( INDEX );
sysread INDEX, my( $idx ), $len;
close INDEX;

open FILE, "<$oneper" or die "Can't open $oneper for reading: $!";

foreach my $lineNum (sort {$a cmp $b} keys %todo) {
  my $offset = unpack 'N', substr $idx, $lineNum * 4, 4;
  print "offset is $offset for linenum $lineNum\n<br>";
  seek FILE, $offset, 0;
  my $line = <FILE>;
  print "found line $line\n";
}