anchor.diff:  HEX
   :
      '0x' F_HexDigit+
  -;
  -
  -SHA1_HASH
  -:
  -   'sha1' ' ' F_Digit+ ' ' F_HexDigit+
  -;
  -
  -DES_HASH
  -:
  -   'des' ' ' F_Digit+ ' ' F_HexDigit+
   ;
   
   IP_PREFIX
  
positive.code: SFLOW
  :
     'sflow'
  ;
  
  SHELL
  
negative.code:    'deny'
  ;
  
  DES
  :
     'des' -> pushMode(M_DES) 
  ;
  
  DES_SHA1
  :
     'des-sha1'
  