Perhaps $File::Find::prune will work:

sub dir_names {
    # Skip over everything that is not a directory.  Note that
    # chdir means we can use -X file tests on default $_.
    -d or return;

    # Skip over directories that don't match required pattern.
    # Match against $_ instead of entire directory path.
    /^[IPD]\d{8}$/ or return;

    print "$File::Find::name\n";

    # Do not recurse below current directory.
    $File::Find::prune = 1;
}
[download]