Ok, I'm cheating but what the heck ...

use Data::Dumper qw/Dumper/;
$_ = "aaaabbbcccccdd eeef";
print Dumper([
    keys %{{ split /(?<=(.))(?!\1)/x }}
]);
__END__
$VAR1 = [
          'ccccc',
          'eee',
          'aaaa',
          ' ',
          'bbb',
          'dd',
          'f'
        ];
[download]

Any comments ?