anchor.diff:  
   IMPORTANT: The single quote (`'`) character is reserved for future use. You
   cannot use an escaped single quote (`\'`) for literal strings. Use an escaped
  -double quote (`\"`) instead. 
  +double quote (`\"`) instead.
   
   [discrete]
   [[eql-syntax-raw-strings]]
  
positive.code: 
  [source,eql]
  ----
  <   <=   ==   !=   >=   >
  ----
  
  `<` (less than)::
  
negative.code: Returns `true` if the value to the left of the operator is less than or equal to
  the value to the right. Otherwise returns `false`.
  
  `==` (equal, case-sensitive)::
  Returns `true` if the values to the left and right of the operator are equal.
  Otherwise returns `false`. For strings, matching is case-sensitive.
  
  `:` (equal, case-insensitive)::
  Returns `true` if strings to the left and right of the operator are equal.
  Otherwise returns `false`. Matching is case-insensitive and can only be used to
  compare strings.
  
  [IMPORTANT]
  ====
  Avoid using the `==` or `:` operators to perform exact matching on
  <<text,`text`>> field values.
  
  By default, {es} changes the values of `text` fields as part of <<analysis,
  analysis>>. This can make finding exact matches for `text` field values
  