Second Try. I am going off to bed after this, my benchmarking tells me this is faster than my previous try:

use strict;
use Data::Dumper;

my $string ='    aaaa    bbbbccccccccbbbb   aaaabbbbbcdddddddddddddddd
+dddd';
my @bah;

while ($string =~ /((.)\2*)/g) {
     push (@bah, [$2,$-[1],$+[1] - $-[1]]);
}

print Dumper(\@bah);
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Update Changed the \2+ to \2* or it would have failed when there was a series one character long.

-enlil