Instructor: Let bindings are mutable by default. We can make them mutable using a reference to wrap the actual value. Basically, a reference is like a box, and the content inside can change.
To update the reference, we can use a column followed by an equals sign. We here refer to the name. The content of our foo changed to six.
In order to retrieve the value of a reference, we can use the carrot character. References, for example, can be used to store the state of the whole game where you are, like this.
Keep in mind to use this feature sparingly to avoid unexpected behavior. Immutability comes with lots of benefits, and you better not give them up without any good reasons.