while (<DATA>)
{
  my @Data = split ( /\s+/ );
  print "Compare $Data[2] and $Data[5].\n";
}
__DATA__
  50545  4.393864E+00  .0   50546  9.589456E+00  .0
  50547  2.690474E+00  .0   50548 -1.668896E+01  .0
  50549 -3.391918E+01  .0   50550 -3.634581E+01  .0
  50551 -3.176630E+01  .0   50552 -1.747830E+01  .0
  50553 -5.256684E-01  .0   50554  1.135265E+01  .0