109876543210
    GNNTCGANNTT
      *     *

return value 2 and 8

##</code><code>##

   109876543210
    GAATCGNNNTT
            *

return value 2 

##</code><code>##

   109876543210
    GANNCGNNNNN
       *      *

return value 0 and 7 

##</code><code>##

my $str = "GNNTCGANNTT";
my @char_arr = split (//,$str);
my $slen = length $str;

foreach my $id (0 .. $#char) {
   if ($str[$id] =~ /N/gi) {
     # not sure how to go from here
    }
}