use Data::Dumper;
my $string ='    aaaa    bbbbccccccccbbbb   aaaabbbbbcdddddddddddddddddddd';
my (@res, $i);
$i = 0;
while ($string =~ /(.)\1*/g) {
push (@res, [$1,  $i, pos($string)-$i]);
$i = pos($string);
}

Dumper (\@res);