Elixir sidesteps these problems. In Elixir, all values are immutable. The most complex nested list, the database record—these things behave just like the simplest integer. Their values are all immutable.
In Elixir, once a variable references a list such as [1,2,3], you know it will always reference those same values (until you rebind the variable). And this makes concurrency a lot less frightening.
But what if you need to add 100 to each element in [1,2,3]? Elixir does it by producing a copy of the original, containing the new values. The original remains unchanged, and your operation will not affect any other code holding a reference to that original.
This fits in nicely with the idea that programming is about transforming data. When we update [1,2,3], we don’t hack it in place. Instead we transform it into something new.