while (defined(my $subdir = glob 'antarctica/*')) {
    next unless -d $subdir;
    chdir $subdir;
    for ...
    chdir '../..';
}

##</code><code>##

opendir my $D, 'antarctica' or die $!;
while (defined(my $dir = readdir $D)) {
    $dir = "antarctica/$dir";
    next unless -d $dir;
    chdir $dir;
    for ...
    chdir '..';