Thanks Corion. I already had the feeling that the sequence somehow is the issue.

Unfortunately providing binmode after IO::Uncompress did not help.

My changed code:

    open my $in, '<:raw', $filename or die "Can't read $filename: $!\n
+";
    if ($filename=~/\.gz$/) {
        $in= new IO::Uncompress::Gunzip $in, { AutoClose => 1 };
    }
    binmode $in, ':utf8';
[download]

It still works with uncompressed and not with compressed data.

Seems I will have to manually decode each line…