foo.rb

puts "toplevel Module nesting: #{Module.nesting.inspect}"

class Foo
  def bar
    puts "hello from Foo#bar"
  end
end

::ExportedFoo = Foo

main.rb

puts "-----> using `require`"
require "./foo"

foo = Foo.new
foo.bar

Object.send :remove_const, :Foo
Object.send :remove_const, :ExportedFoo

####

puts
puts "-----> using `load` with module wrapping"
load "./foo.rb", true

begin
  foo = Foo.new
rescue
  puts "can't load Foo, trying ExportedFoo"
end

foo = ExportedFoo.new
foo.bar

__END__
Result:

$ ruby main.rb
-----> using `require`
toplevel Module nesting: []
hello from Foo#bar

-----> using `load` with module wrapping
toplevel Module nesting: [#<Module:0x007f8d7b1096a8>]
can't load Foo, trying ExportedFoo
hello from Foo#bar