my $dir = "/opt/DSPKG";
opendir(my $bin_dh, $dirs)
   or die "Can't open directory $dir: $!\n";

my @subdirs = grep { !/^\.\.?\z/ && -d "$dirs/$_" }
              readdir $bin_dh;

my $pkg_file = '/tmp/pkgtest';
open(my $pkg_fh, '>', $pkg_file)
   or die "cant open pkgtest $pkg_file: $!\n";

foreach my $subdir (@subdirs) {
   print $pkg_fh "$subdir\n";
}