local static variable in Ruby, using file local scope.

local_static_variable2.rb

# g.rb
cache = ""
klass = class<<self; self; end
klass.send(:define_method, :foo) do
  lambda {|s| cache += s; cache }
end

# call_foo.rb
require './g'

f = foo
f.call "a"
puts f.call("b")