super_duper.rb

class A
  attr_reader :val
  def initialize(a, &b)
    @val = a || (b ? b.call : :nada)
  end   
end

class B < A
  def initialize(b)
    super(b)
  end
end

# A.new(true).val
# => true
# A.new(false) { :ok }.val
# => :ok
# B.new(true).val
# => true
# B.new(false).val
# => :nada
# B.new(false) { :oops }.val
# => :oops
# How did that happen? `super` implicitly passes block params along even if you don't

class C < A
  def initialize(c)
    super(c, &nil)
  end
end

# C.new(false) { :ok }.val
# => :nada
# RUBY_DESCRIPTION
# => "ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin10.8.0]"

See also: http://stackoverflow.com/questions/10541242/scrubbing-a-block-from-a-call-to-super/10541349#10541349