anchor.diff:  [[eql-syntax-strings]]
   ==== Strings
   
  -Strings are enclosed with double quotes (`"`) or single quotes (`'`).
  +Strings are enclosed with double quotes (`"`).
   
   [source,eql]
   ----
   "hello world"
  -"hello world with 'substring'"
  -----
  +----
  +
  +Strings enclosed in single quotes (`'`) are not supported.
   
   [discrete]
   [[eql-syntax-wildcards]]
  
positive.code: `nested` field mappings are otherwise supported.
  
  [discrete]
  [[eql-unsupported-syntax]]
  ==== Unsupported syntax
  
  
negative.code: |`\t`             | A tab character
  |`\\`             | A backslash (`\`) character
  |`\"`             | A double quote (`"`) character
  |====
  ====
  
  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. 
  
  [discrete]
  [[eql-syntax-raw-strings]]
  