Hi Marshall,

Thanks for the code. I did changed the code a bit to make it work. Now, I am getting the correct output file.

while (my $row = $csv->getline($FILE1)) 
{
                        # $row is a reference to a row
    my @fields = @$row; # this explicitly de-references
    my $id1 = $fields[1];
    
    if (exists $file2{$id1})
    {
    my $fields_ref=  \@fields;
    unshift(@$fields_ref, "HK");
    $csv->print ($FILE3, $fields_ref);
       # $csv->print ($FILE3, "HK", @fields); #both files
    }
    else
    {
    my $fields_ref = \@fields;
    unshift (@$fields_ref, "NOT_HK");
    $csv->print ($FILE3, $fields_ref);
    }
  }
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