I don't have time to look at it personally, at least not now, but the following will help you greatly. Change

   open ($testdataset, "datasetnew.txt") or die "Cannot open file";
   @testdataset =  <$testdataset>;
   close ($testdataset);

   @testdataset = grep { $_ ne '' } @testdataset;
   @testdataset = grep /\S/, @testdataset;
  
   foreach $dataline (@testdataset) {
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to

   open (my $testdataset, '<', "datasetnew.txt")
      or die "Cannot open input file: $!\n";

   while (my $dataline = <$testdataset>) {
      next if $dataline =~ /^\s*$/;
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You'll have (2 or 3) fewer copies of your file in memory.