Can you give us 10 example lines from the file?

You can do something like:

my $filecounter = 0;
open INPUTFILE, "InputFile";
open OUTPUTFILE, "outputfile.$filecounter";
while (<INPUTFILE>) {
  if ($. % 1000000) {
      close OUTPUTFILE;
      $filecounter++;
      open OUTPUTFILE, "outputfile.$filecounter";
   }
   print OUTPUTFILE $_;
}
[download]

If one ">" per line.. but example data would make it easier to tell how robust the split has to be.

Waswas-fng