Constant leaking on class_eval

console.rb

[arthurnn@snowball ~]$ irb
irb(main):001:0> class Foo
irb(main):002:1> FOO = "foo"
irb(main):003:1> end
=> "foo"
irb(main):005:0> Foo.class_eval { BAR = "bar" }
=> "bar"
irb(main):006:0> BAR
=> "bar"
irb(main):007:0> FOO
NameError: uninitialized constant FOO
	from (irb):7
	from /Users/arthurnn/.rubies/ruby-github/bin/irb:15:in `<main>'
irb(main):008:0> Foo::FOO
=> "foo"
irb(main):009:0> Foo::BAR
(irb):9: warning: toplevel constant BAR referenced by Foo::BAR
=> "bar"
irb(main):010:0>