while(...){
    @data= split ("\t", $line);  
                            
    $curr_identifier= $data[0];
    $markername= $data[1];
    $position1= $data[2];
    $height= $data[4];

    if ($line >0){
         $result[0] = $markername;
         $result[1] = $position1;
         $result[2] = $height;
         $result[3] = $curr_identifier;

         $data{$curr_identifier}= [@result];
     }
}

##</code><code>##

  if (!defined $data{$curr_identifier}[2]){
            $output1= "no height for both markers- failed";
 } else {
    if ($data{$curr_identifier}[2] eq " ") {
        $output1 = $markername;

    } 
 }
 
 print $curr_identifier, $output1 . "\t" . $output1 . "\n";