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

opendir my $D, 'antarctica' or die $!;
while (defined(my $dir = readdir $D)) {
...
    chdir $dir;
    for ...
    chdir '..';