ExifTool Perl Library Module: How to separate keyword- from subject-values - perl

Question

I am using ExifToolVersion : 9.13 to read out metainformations of a pdf-file to formfields, where users can edit the values.
With a second perl-script I write these changed values back to the file.
That works fine with the exception, that subject-values appear in keyword-tags and keyword-values in subject-tags, although I write the new values explizite to each tag.
$exifTool->SetNewValue($tag[$i], \#keywords, Replace => 1);
$exifTool->SetNewValue($tag[$i], $file_beschreibung, Replace => 1);
$exifTool->SetNewValue($data[$i]=>\#keywords, Group0 => 'PDF');
$exifTool->SetNewValue($data[$i]=>$file_beschreibung, Group0 => 'PDF');
I tried to write an empty value to the XMP tags, but that doesn't work
$exifTool->SetNewValue($data[$i]=>$leer, Group0 => 'XMP');
Is there a way to to avoid the concatenation of both values?

Answer 1

I now found, that I have to clear all XMP-Tags
my #data = ("Author","Keywords","ModifyDate","Rights","Title","Subject");
my $elemente = #data;
for ($i=0; $i<$elemente; $i++)
{
if ($i==1)
{
if (my $tagname =~ m/^XMP-.*:$data[$i]/)
{
$exifTool->SetNewValue($tagname=>'', Group => 'XMP');
}
$exifTool->SetNewValue($data[$i]=>\#keywords, Group => 'PDF');
}
if ($i==5)
{
my $tagname = "XMP-dc:".$data[$i];
$exifTool->SetNewValue($tagname=>'', Group => 'XMP');
$exifTool->SetNewValue($data[$i]=>$file_beschreibung, Group => 'PDF');
}
}
This works fine. Thank you for helping!