problem on ire with lambda and variable

After a "specific" Labda the variable foo unbound.

# ire
Reia Interactive Shell (prerelease)
Running on Erlang (BEAM) emulator version 5.6.5 [source] [async-threads:0] [hipe] [kernel-poll:true]
>> foo=4
=> 4
>> foo
=> 4
>> f1 = fun(x, y) { x + y }
=> #<Lambda -expr/5-fun-3- (module: erl_eval arity: 2>
>> foo
=> 4
>> plus_two = fun(n) { n + 2 }
=> #<Lambda -expr/5-fun-2- (module: erl_eval arity: 1>
>> foo
exception error: variable '_foo_0' is unbound
>> foo
exception error: variable '_foo_0' is unbound
>> bar=1
=> 1
>> foo
=> 4