use File::Path qw(remove_tree);

chdir("$MEDIA_DIR"); # absoluter Pfad 
opendir(DIR, ".") || die $!;
@entries = readdir(DIR);
closedir(DIR);
foreach (@entries) {
	# Hier habe ich die "."-Ordner "vergessen"
	remove_tree("$_") unless defined $media{"_$_"};
}