-If List A contains entries in List B return bool (if List A contains at least preexisting entries in list B)
-If List A equals List B then return Bool
-Dedup List entries, return list.
-List combine, return list.

• Already possible using the reduce operator
• This is the equal operator
• Not possible yet, might implement is as the uniq operator
• This has been implemented in-dev as the concat operator.