Removing instance variables

@new_user = User.find(:first)
.
.
@old_user = remove_instance_variable(:@new_user)
# @new_user is nil now
------------------
More:
- http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/20911
- Page 555 of pickaxe book under Object (or search for string remove_instance_variable)