extension 1
-----------

   (?\d[<class>]) allows to override \d
   (?\s[<class>]) ...                \s
   (?\w[<class>]) ...                \w

e.g.
----
(?x)

(?\s[_])       # underline
(?\d[IVXLCDM]) # roman
(?\w[--])  # lowers only

(\d+)          # MDCLXVII
 \s+
(\w+)          # 
 \s+
(\w+)          # ਬ᪮
 \s+
(\w+)          # ᫮
 \s+
                 1667

---------------------------------
MDCLXVII___ਬ᪮_᫮__1667

note 1: although 0..9 are included both in \d and \w,
        their presence in those classes
        handled independently

        e.g. setting \d to [#] not removes 0..9 from \w

note 2: /i handled independently

note 3: to define \D use (?\d[^<class>])
                  \S use (?\s[^<class>])
                  \W use (?\w[^<class>])

extension 2
-----------

   added \v

extension 3
-----------

   added \< and \>

extension 4
-----------

   866-table Russian letters are included in \w and handled by /i

fix 1
-----

   #-comments

feature 1
---------

   If ?+*{} placed after comment block or after space (x mode),
this quantifier applied to entire literal string that before
instead single char

optimization 1
--------------

   January|February|March|April and likes are optimized

## EOF
