Oh rapture!  Oh, delicious zesty snacks!  Oh, steamed uncles in a cabbage
display!  OH, LAMB MEDALLIONS! 

For serious: I am outstripped with zeal.  The sandbox is open.  While still
in primitive fashion, it's pretty hot for being eleven hours old.

  gem install sandbox --source code.whytheluckystiff.net

This module swaps in a new symbol table, so you can basically manage multiple
interpreters at once.  There are so many possibilities for using this.  For
emulating selector namespaces, for jailing code.

  >> s = Sandbox.new
  >> s.eval("module Hidden; end")
  => nil
  >> Hidden
  NameError: uninitialized constant Hidden

There's more explanation elsewhere[1], but if you want to see the hack for
yourself, I'd hit ext/sand_table/sand_table.c[2].  Thanks go to MenTaLguY for
helping me conceive the hack and hope there is some among you who will see something
good in this and help me batter it into warm, submissive donuts.

_why

[1] http://redhanded.hobix.com/inspect/theThrillingFreakyFreakySandboxHack.html
[2]
http://code.whytheluckystiff.net/svn/sandbox/trunk/ext/sand_table/sand_table.c