use Data::Dumper;
my $str = "aaabbccccdd eee";

my $last = '';
my @res;
my $i = -1;
for my $chr ( split //, $str ) {
    $i++ unless $chr eq $last;
    $res[$i] .= $chr;
    $last = $chr;
}

print Dumper \@res;

__DATA__
$VAR1 = [
          'aaa',
          'bb',
          'cccc',
          'dd',
          ' ',
          'eee'
        ];