use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(qr/[^\d\D]/)->explain;
__END__
The regular expression:

(?-imsx:[^\d\D])

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  [^\d\D]                  any character except: digits (0-9), non-
                           digits (all but 0-9)
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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any character except digits and non-digits is every character.