Understanding code: Kernel#require and blocks.

I'm trying to debug a Rails application which complains about an
undefined constant when `rake db:migrate` is invoked.  The rakefile
that comes with rails modifies $:, then does several more requires.
Given the length of $: it is tedious to find which files are
require`d.   Clearly this is not a rails specific difficulty: it is
common to understanding anyone's code making sufficiently extensive
use of require.  So my question is this:
Would it be practical to modify require so that it accepts a block, 
to which it would pass the path of the object it successfully
require`d?  Then, to find the files I must read to understand what
is happening I could change

-  require 'tasks/rails'
+  require 'tasks/rails' {|path| $stderr.puts "require`d #{path]"}

        Hugh