use Data::Dump 'pp';

my @dirs = qw(
    tmp/a tmp/a/b tmp/a/b/c tmp/a/b/c/e tmp/a/b/d tmp/a/b/d/g
    tmp/a/b/d/g/h tmp/a/b/d/g/i tmp/a/b/k
);

my %empty;
for (@dirs) {
    $empty{$_} = 1;    # assume empty
    s!/[^/]+$!!;       # find parent
    delete $empty{$_}; # and remove it
}
pp keys %empty;
__END__
("tmp/a/b/k", "tmp/a/b/d/g/h", "tmp/a/b/c/e", "tmp/a/b/d/g/i")