$ perl -E 'my $test_rec = "X" x 45; open my $fh, ">", "test_data"; $fh->say($test_rec) for 1..769114;'

$ ls -l test_data
-rw-r--r-- 1 ken None 35379244 Jan 23 17:09 test_data

$ wc test_data
  769114   769114 35379244 test_data

$ head -1 test_data
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX