Alphabetic
   {_a} == [[:alpha:]] (== [A-Za-z] in US)
  Brackets
   {_b} == [{}()[\]<>]
  Control Character
   {_c} == [[:cntrl:]] (== [\x001-\x01f\x07f] in US)
  Digit
   {_d} == [[:digit:]] (== [0-9] in US)
  Exponent
   {_e} == [DdEe][-+]?{_d}{1,3}
  Floating Point Number
   {_f} == [-+]?({_d}+\.{_d}*|{_d}*\.{_d}+)
  Float, Optional Exponent
   {_g} == {_f}({_e})?
  Hexadecimal Digit
   {_h} == [[:xdigit:]] (== [0-9A-Fa-f] in US)
  Integer
   {_i} == [-+]?{_d}+
  Alpha-Numeric
   {_n} == [[:alnum:]] (== [A-Za-z0-9] in US)
  Octal Digit
   {_o} == [0-7]
  Punctuation
   {_p} == [[:punct:]] (== [\!-/:-@[-`{-\x07f] in US)
  Double or Single Quote
   {_q} == {_s}["'`]
  Real Number
   {_r} == [-+]?({_d}+(\.{_d}*)?|{_d}*\.{_d}+){_e}
  Zero or Even Number of Slashes
   {_s} == (^|[!\\](\\\\)*)
  Printable Character
   {_t} == [[:print:]] (== [\s-~] in US)
  Graphical Character
   {_u} == [[:graph:]] (== [\x01f-~] in US)
  White Space
   {_w} == [[:blank:]] == [\s\t]
  Expanded White Space, \t, \n, \v, \f, \r, \s
   {_z} == [[:space:]] == [\t-\r\s]