Ruby

Given an open irb session. After exiting from binding.irb the _, which is the last value of the current context, somehow retains the value of the last expression evaluated in the context of binding.irb and then doesn't change it. This never happens to the irb subshell in an open irb session.

Steps to reproduce:

1. Fire up irb.
2. Type binding.irb.
3. Get out of the current context by pressing Ctrl-D.
4. Type anything simple like 1+3.
5. Type _ to see 4, receive nil instead.

Another example:

1. Fire up irb.
2. Type binding.irb.
3. Type any expression to evaluate like 1+3.
4. Get out of the current context by pressing Ctrl-D.
5. Type anything simple like 1+4.
6. Type _ to see 5, receive 4 instead.