$ perl -Mstrict -Mwarnings -E '
say join q{-}, do {
   my %seen;
   grep { not $seen{ $_ } ++ } split m{-};
   } for qw{
      12-12
      12-12-12
      12-13-12-13
      12-12-13-13
      12-13-13-14
      };'
12
12
12-13
12-13
12-13-14
$