Ruby » Backport86

class ZeroDivisionError
  def self.new(message)
    puts 'new ZeroDivError'
    'not an exception'
  end
end

module Any
  def self.===(other)
    puts "?#{other.inspect}"
    true
  end
end

begin
  1/0
rescue Exception, Any
  puts "rescue"
  p $!
ensure
  puts "ensure"
end

puts 'Done'

=====

The output is:
new ZeroDivError
ensure

This means that if a non-Exception is returned from the new method above, the stack is magically unwound ignoring all rescue clauses (=== is not called) and no error message is displayed at all.

The same behavior can be observed in both:
ruby 1.8.6 (2008-08-11 patchlevel 287) [i386-mswin32]
ruby 1.9.1p129 (2009-05-12 revision 23412) [i386-mswin32]