When you have an immutable OCL expression, you always return a value - and then the OCLOperators_caseTrueFalse is good. However, when using the MDriven Action-Language that allows updates of objects, another construct is introduced to compact things even more:

boolean.whentrue(dothis):boolean

The return is always the arg0.

Example:

let x=SomeObject.SomeEnum in (  
  (x=#Enum1).whentrue(SomeObject.DoYourThing1);  
  (x=#Enum2).whentrue(SomeObject.DoYourThing2);  
  (x=#Enum3).whentrue(SomeObject.DoYourThing3) 
)

Fun fact: "whentrue" and logical "and" are implemented the same - the logical "and" only evaluates arg1 of arg0 is true (lazy evaluation) and "whentrue" does the same thing, but always returns arg0.

This means that a convoluted but equivalent construct can be:

let x=SomeObject.SomeEnum in (  
  (x=#Enum1) and (SomeObject.DoYourThing1;true);  
  (x=#Enum2) and (SomeObject.DoYourThing2;true);  
  (x=#Enum3) and (SomeObject.DoYourThing3;true) 
)