interesting_locals_ast.rb

class Binding
  def set(hash)
    backup = Thread.current[:binding_set]
    hash.each do |var, val|
      Thread.current[:binding_set] = val
      eval(%(#{var} = Thread.current[:binding_set]))
    end
  ensure
    Thread.current[:binding_set] = backup
  end
end

# TOGGLE ME:
# a = nil

b = Kernel::binding

b.set(:a => 1)

p b.send :local_variables
p Kernel::binding.send :local_variables
p local_variables
p eval('a', Kernel::binding)
p a