anchor.diff:  
   Vars are associations between a name (a symbol) and a value. Vars in a namespace have a fully-qualified name that is the combination of the namespace name and the var name. For example, `clojure.string/join` is a fully-qualified var name where `clojure.string` refers to the namespace and `join` refers to the var inside the namespace. All vars are globally accessible via their fully-qualified name. By convention vars have lower case names with `-` separating words, although this is also not required. Var names may contain most non-whitespace characters.
   
  -Vars are created using `def` and other special forms or macros that start with `def`, like `defn`. Vars are created in the "current" namespace. The Clojure runtime tracks the current namespace in the var `clojure.core\*ns*`. The current namespace can be changed using the `in-ns` function.
  +Vars are created using `def` and other special forms or macros that start with `def`, like `defn`. Vars are created in the "current" namespace. The Clojure runtime tracks the current namespace in the var `pass:[clojure.core/*ns*]`. The current namespace can be changed using the `in-ns` function.
   
   === Loading
   
  
positive.code: 
  * `clojure.set` - just loads `clojure.set` namespace (if not already loaded)
  * `[clojure.set :as set]` - load and create an alias `set` for the namespace `clojure.set`
  ** This allows you to refer to vars in set with for example `set/union` instead of `clojure.set/union`
  * `[clojure.set :refer [union intersection]]` - load and refer specific vars into this namespace
  ** This allows you to use just `union` instead of `clojure.set/union`
  
  
negative.code: The `:require` class corresponds to the `require` function which specifies one or more namespaces to load that this namespace depends on. For each namespace, `require` can do several things:
  
  * Load (or reload) the namespace
  * Optionally assign an _alias_ that can be used to refer to vars from the loaded namespace only in the scope of this namespace
  * Optionally _refer_ vars from the loaded namespace for use by unqualified name in this namespace
  
  The last two parts are all about making names easier to use. While vars can always be referred to by their fully-qualified name, we rarely want to type fully-qualified names in our code. Aliases let us use shorter versions of longer fully-qualified aliases. Refer allows us to use names without a namespace qualifier at all.
  
  