Display / Proc.
If the evaluation type "is_in" (see eval) is used for evaluation, then the characters in the input string should be found in this string as well. This value is also passed as argument to the evaluation function if a user-defined evaluation function is registered.
The "is_in" value is trimmed during processing, leading and trailing whitespaces are removed. If whitespaces should be allowed, it should be in between other characters, example