anchor.diff:  (Required, string or `null`)
   Substring to search for. If `null`, the function returns `null`.
   
  -If using a field as the argument, this parameter only supports the following
  +If using a field as the argument, this parameter supports only the following
   field datatypes:
   
   * <<keyword,`keyword`>>
  
positive.code: Source string. Empty strings return an empty string (`""`), regardless of the
  `<left>` or `<right>` parameters. If `null`, the function returns `null`.
  
  If using a field as the argument, this parameter only supports the following
  field datatypes:
  
  * <<keyword,`keyword`>>
  
negative.code: String for which to return the character length. If `null`, the function returns
  `null`. Empty strings return `0`.
  
  If using a field as the argument, this parameter supports only the following
  field datatypes:
  
  * <<keyword,`keyword`>>
  