I&#x27;m not sure that&#x27;s really true, but it regardless misses the point. No matter what language you&#x27;re using, you&#x27;ll eventually need to be able to deal with multiple versions of it.<p>Even if you&#x27;re running an operation small enough that you can upgrade every single runtime in use all in one step, you&#x27;ll still need to have two versions around while you test. But many, many places have to deal with multiple language versions simultaneously. E.g., if you maintain an open source library and have any regard for your users, you have to test how it behaves in multiple language versions.