is_enum_value Yes Returns FALSE if the provided value is not one of an accepted list. The arguments are a comma delimited list. Each argument can be a single value or carat (^) delimited list.
When the provided value is not in the list the error message will display the values that were expected.
The first (or only) value is one that is part of the list to accept
The second value (if used) is the text to display when the provided value is not in the list of accepted values. The second value can be prefixed with "lang;" to use a language directive instead of direct text.

    is_enum_valueif
      [acceptable_value1
      ,acceptable_value2^Alterative text
      ,acceptable_value3^lang:language_directive
      …
      ]