Yes ... that's because you changed the regexp in the grep, it should be

  preprocess => sub {
    ## added ^ and $
    return grep { not(-d and /^dir(?:One|Two|Three)$/) } @_
  },
[download]

See. your local perlre for more info on alternations (the | metacharacter), and anchors (as seen by the ^ and $ in the regexp).
HTH

_________
broquaint