Eeepub gem warnings?

I am using the fabulous eeepub gem to convert a folder full of HTML
files into a valid epub package. It works swimmingly, except I get the
following errors with each turn of my loop:

Minogue_0089 split into chapters…
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/
container_item.rb:19: warning: instance variable @depth not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/
container_item.rb:19: warning: instance variable @total_page_count not
initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/
container_item.rb:19: warning: instance variable @max_page_number not
initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/maker.rb:
101: warning: instance variable @languages not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/maker.rb:
102: warning: instance variable @subjects not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/maker.rb:
103: warning: instance variable @descriptions not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/maker.rb:
104: warning: instance variable @rightss not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/maker.rb:
105: warning: instance variable @relations not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/
container_item.rb:19: warning: instance variable @unique_identifier
not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/
container_item.rb:19: warning: instance variable @toc not initialized
/opt/local/lib/ruby/gems/1.8/gems/eeepub-0.6.1/lib/eeepub/opf.rb:42:
warning: instance variable @spine not initialized
created Minogue_0089.epub

I see these variables in the respective places where they are defined
– in the initialize method of the various classes – but the really
funny thing is that I don’t get these errors when I run the example
code that comes with the gem. That code begins with a line I don’t
recognize or understand:

$:.unshift(File.dirname(FILE) + ‘/…/lib’)

followed by:

require ‘rubygems’
require ‘eeepub’

I am running this from the command line, and my script begins with:

#!/usr/bin/env ruby -wKU
require ‘rubygems’
require ‘nokogiri’
require ‘cgi’
require ‘fileutils’
require ‘open-uri’
require ‘eeepub’

Can anyone explain what the $:.unshift bit does? And is there a way to
just hide these warnings? The script seems to work just fine.

Walter