.
.
opendir D, $opts{d} or die ...;
.
.
foreach my $file (readdir D)
{
  my ($filebase, $dirname, $ext) = fileparse($file, '\..*');
  my $csvFile = "$opts{d}\\$filebase.csv";
  open FILE_OUT, ">$csvFile" or die ...;
  .
  .
  foreach my $parent (@parents)
  {
    print FILE_OUT $parents{$parent} . "\n";
  }
  close FILE_OUT;
}