Is it possible in rails to change the value of a class variable in a plugin?

Question

ruby

I'm trying to refactor the code, but the question arose of how to change class variables in modules defined in mixins.
I tried to wrap everything in the method in Proc, return Proc and call it through self.instance_exec user, folder, &block before converting it to a block. However, the @@user class variable has not changed.
When debugging a method called by proc, the value is set, but disappears upon exit.
I set the @@user variable to nil before the method, in theory, does the block change already defined variables?