#!/usr/bin/perl
use strict;
use warnings;

my $string = 'AAAA TTT GGGG CCCC AAAAAA CCCC ABAB CCC TTT TTTT GGGEGEE';

while ($string =~m/\b((\w)\2{2,6})\b/g)
{
    print "$-[1] $1 \n";   
}

__END__

#prints
0 AAAA  
5 TTT  
9 GGGG  
14 CCCC  
19 AAAAAA  
26 CCCC  
36 CCC  
40 TTT  
44 TTTT