Have you considered what ->addTree is actually doing? It is not a function that purely returns information.

I think you should rethink your approach and consider getting two lists, one list of the files in the archive and one list of the files not in the archive, then eliminate the members in both lists (see perlfaq4) and then add the appropriate number of remaining files to the archive.

Thank you for your reply. You're right. But

@files = $zip->memberNames();
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does exactly what I want. I have all the file names and paths in the array. And with:

@file = splice @files, 1, 50;
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I reduce the information before it's written to an archive. I want to select before I write and have the names, that's why comparing is not my goal. It's curious why

foreach $line (@file) {

   $fileend = (split(/\./,"$line"))[-1];
    if (($fileend eq "jpg") || ($fileend eq "txt")) {
       $zip->addFile("$line");
      
  }
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doesn't do the job. Any explanation to this?

Your program as shown still contains the line:

@files = $zip->addTree( "$zippath" );
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This will always add all files.