c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my $s = 'abcdefghijklmno';
 ;;
 my $validate = qr{ \A (....) (..) (..) (.....) (..) \z }xms;
 ;;
 my @ra = Suc($s, $validate);
 dd \@ra;
 ;;
 sub Suc {
   my ($DC, $rx_valid) = @_;
   ;;
   my @ra = $DC =~ $rx_valid;
   @ra or die qq{bad format: '$DC'};
   ;;
   return map uc($_), @ra;
   }
"
["ABCD", "EF", "GH", "IJKLM", "NO"]