Just check for them. In your original code:

foreach (@data) {
  next if $_ eq "." || $_ eq "..";
  push @dir, $_ if -d "./desktop/$_";
}
[download]

Using grep:

@dir = grep { $_ ne "." && $_ ne ".." && -d "./desktop/$_" }
    readdir(TEXTFILES);
[download]

--ZZamboni