So, I'm struggling with the syntax of a formula to create some buckets or groups.

When the value of a text field contains, X, Y, Z, etc., return X, Y, Z, etc. 

Field - Plan Group:

Formula(theoretical):

Case( Plan_Name__c,
Contains(Plan_Name__c, "X"), "X",
Contains(Plan_Name__c, "Y"), "Y",
...

Does anyone know a clean way to write this into a formula? I have about 6-7 groups that I am trying to create.