sub lcssw {
   my ($s1, $s2) = @_;

   my $i;
   my %codes;
   my %words;

   for ($s1, $s2) {
      $_ = join '',
           map { $codes{$_} = chr(++$i) if !exists($codes{$_});
                 $codes{$_}
               }
           $_ =~ /\w+/g;
   }

   my $lcss = lcss($s1, $s2);
   $lcss = "" if (!defined $lcss);

   @words{values %codes} = keys %codes;
   return join ' ', @words{ $lcss =~ /./sg };
}