use strict;
use warnings;
use List::UtilsBy::XS qw(nsort_by);

my $string = "AAATTTAGTTCTTAAGGCTGACATCGGTTTACGTCAGCGTTACCCCCCAAGTTATTGGGGACTTT";
my @matches;
push @matches, $& while ($string=~m/([AGCT])\1+/g);
local $, = "\n";
print nsort_by {length} @matches ;