You can also use conditional fail expressions.
They look like this:
expression1 : expression2 : expression3 : ... : expressionN;
This conditional fail expression may be used for mapping, assignment to a variable and as an argument of a function too.
The expressions are evaluated one by one, starting from the first expression and going from left to right.
As soon as one of these expressions is successfully evaluated, it is used and the other expressions are not evaluated.
If none of these expressions may be used (assigned to a variable, mapped to the output field, or used as an argument), the graph fails.
Remember that in CTL2 this expression may be used in multiple ways: for assigning to a variable, mapping to an output field, or as an argument of the function.
(In CTL1 it was only used for mapping to an output field.)
Also remember that this expression can only be used in the interpreted mode of CTL2.