c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my $s = '04abcdefgh06ABCDEFGH05tuvwxyz';
 my @caps =
   map join('', m{ \A (\d\d) }xms, m{ ([[:alpha:]]{$1}) }xms),
   $s =~ m{ \G \d\d [[:alpha:]]+ }xmsg
   ;
 dd @caps;
"
("04abcd", "06ABCDEF", "05tuvwx")