Rails core - Dec 2005 - what on earth is happening here

there is some seriously black art happening here:

i added the following code to callbacks.rb

     def self.append_features(base) #:nodoc:
       super

$i ||= 0
p $i
p caller.last
$i += 1

       ...
       ...
       ...

and then fired up ./script/console.  this is what it prints:

   harp:~/ror/bug > ./script/console
   0
   "./script/console:2"
   Loading development environment.
   0
   "/home/ahoward/bin/irb:13"
   ...

how on earth is that possible!?  what has been done?  just to illustrate it
would be as if this code:


     harp:~/ror/bug > cat a.rb
     module M
       def self::append_features other
         $i ||= 0
         p $i
         p caller.last
         $i += 1
       end
     end

     class C
       include M
       include M
     end

printed out ''0'' and then ''0'' but, of course,
it does not:

     harp:~/ror/bug > irb -r a.rb
     0
     "/home/ahoward/bin/irb:13"
     1
     "/home/ahoward/bin/irb:13"


can someone shed some light on this?

-a
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