use strict;
use warnings;

my @data = qw/a mnk ab m b bc abcd cd bcd bd m nk /;

@data = sort { length($a) <=> length($b) } @data;

my %result;

foreach my $word (@data) {
   my $uc_word = uc($word);
   my $partial_word;

   foreach my $start_letter (1..length($uc_word)) {
      foreach my $num_letters ($start_letter..length($uc_word)-$start_letter+1) {
         delete($result{substr($uc_word, $start_letter-1, $num_letters)});
      }
   }

   $result{$uc_word} = $word;
}


print join(",", values(%result));