while (defined($long_file_name = readdir(DIR))) {
   my $short_path = Win32::GetShortPathName("$dir\\$long_file_name");
   (my $short_file_name = $short_path) =~ s#^.*[\\/]##;
   ...
}
[download]

For fun,

$dir = ...;
@files = map { (split(' ', substr($_, 39)))[0] }
            split("\n", `dir /x "$dir"`);
[download]

will also do the trick.