#!/usr/bin/perl 
 
my $l=600_000; 
 
while (1) { 
  print "\rTesting $l..."; 
  open OUT,">biglines.txt" || die; 
  print OUT "x" x $l; 
  close OUT; 
 
  open IN,"<biglines.txt" || die; 
  my $r=<IN>; 
  close IN; 
 
  if (length($r)!=$l) { 
    print "Oops! A linelength of $l fails!!\n"; 
    exit; 
  } 
  $l+=5000; 
}