Try this:

#!/usr/bin/perl -w
use strict;
use CGI qw(:standard);

print header();

my $data = 'sample.db';
open (PAGE, $data)  or die "Can't open $data: $!";

while (my $line = <PAGE>) {

   my @columns = split "\t", $line;

   if ($columns[2]) {
      print "three = $columns[2]<br>";
      print "four = $columns[3]<br>";
   }
}
[download]