there must be another bug, I've just tested it with 5.6.2

lanx$ perl -de0

Loading DB routines from perl5db.pl version 1.07
Editor support available.

...

  DB<2> $card = join '', 1..9,0..6 

  DB<3> p $CCformatted = join '-', $card =~ /..../g;
1234-5678-9012-3456
  DB<4> p $]
5.006002
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