Push to and pop from the workspace stack in IRB using pushws and popws:
> self
= main
> thing = Object.new
= #<Object:0x007f8eb18b54d8>
> pushws thing
= [main]
> self
= #<Object:0x007f8eb18b54d8>
> def hello; "hey!"; end
= nil
> hello
= "hey!"
> pushws hello
= [main, #<Object:0x007f8eb18b54d8>]
> self
= "hey!"
> popws
= [main]
> popws
= []
> self
= main
> thing.hello
= "hey!"
Defined in irb/ext/workspaces.rb.