         # File lib/rake.rb, line 391
    391:     def lookup(name)
    392:       if @hash.has_key?(name)
    393:         @hash[name]
    394:       elsif ENV.has_key?(name.to_s)
    395:         ENV[name.to_s]
    396:       elsif ENV.has_key?(name.to_s.upcase)
    397:         ENV[name.to_s.upcase]
    398:       elsif @parent
    399:         @parent.lookup(name)
    400:       end
    401:     end