def visit_EnvWrapperNode(node)
      debug_visit(node)
      with_env do
        node.env.each_pair do |env_var_name, arg_node|
          world.env[env_var_name] = process_EnvArgumentNode(arg_node)
        end
        node.node.accept(self)
      end
    end
def visit_EnvWrapperNode(node)
      debug_visit(node)
      with_env do
        node.env.each_pair do |env_var_name, arg_node|
          world.env[env_var_name] = process_EnvArgumentNode(arg_node)
        end
        node.node.accept(self)
      end
    end
Represents a statement that has scoped environment variables being set,
 e.g.:

    yap> A=5 ls
    yap> A=5 B=6 echo

 These environment variables are reset after the their statement, e.g.:

    yap> A=5
    yap> echo $A
    5
    yap> A=b echo $A
    b
    yap> echo $
    5