for my $position (0..(length($reference_str)-length($small_str)))
{
  my $processed_str = $small_str ^ substr($reference_str, $position, length($small_str));
  next unless $processed_str =~ m<(
                                      \0{9}
                                    | \0{1} . \0{8,}
                                    | \0{2} . \0{7,}
                                    | \0{3} . \0{6,}
                                    | \0{4} . \0{5,}
                                    | \0{5} . \0{4,}
                                    | \0{6} . \0{3,}
                                    | \0{7} . \0{2,} 
                                    | \0{8} . \0{1,}
                                  )>xms;
   print("Match found! ", substr($reference_str, $position+pos($processed_str),length($1))) and last;
}