use constant MIN_REPEATS => 2;  # Must have at least this many repeats

my $str = 'aabcdabcabcecdecd';

local our %counts;
$str =~ /(.{2,})(?{ ++$counts{$1} })(?!)/s;
delete @counts{ grep $counts{$_}<MIN_REPEATS, keys %counts };

use Data::Dumper;
print Dumper \%counts;