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


my %uniq=();
my $string = 'ACRMGAHKMAHGTXX';

      substr($string, $_, 10 ) =~ m[([AGTC].{0,8}[AGTC])]
      and ++$uniq{ $1 }
      for 0 .. length( $string )-1;

for my $key (keys %uniq){
	print $key, "\n";
}


#above code outputs the following:
GAHKMAHG
CRMGAHKMA
AHGT
AHKMAHGT
GT
GAHKMAHGT
ACRMGAHKMA

#and I only want the following:
ACRMGAHKMA
GAHKMAHGT