A few ways to do it, for variety:

my $str= "aaabbccccdd eee";
my @list;
my $pos= 0;
while(  $str =~ /(?<=(.))(?!\1)/g  ) {
    push @list, substr( $str, $pos, pos($str)-$pos );
    $pos= pos($str);
}
[download]

my @list= split /(?<=(.))(?!\1)/, "aaabbccccdd eee";
@list= @list[ map 2*$_, 0..@list/2-1 ];
[download]