anchor.diff:  `not in` (case-sensitive)::
   Returns `true` if the value is not contained in the provided list. For strings,
   matching is case-sensitive.
  +
  +`:` (case-insensitive)::
  +Returns `true` if the value is contained in the provided list. Can only be used
  +to compare strings.
   
   [discrete]
   [[eql-syntax-math-operators]]
  
positive.code: 
  [source,eql]
  ----
  field : "example*wildcard"
  field : "*example-wildcard"
  field : "example-wildcard*"
  ----
  
  [discrete]
  
negative.code: `:` (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. Supports <<eql-syntax-wildcards,wildcards>> and
  <<eql-syntax-lookup-operators,list lookups>>.
  
  [IMPORTANT]
  ====
  