>>326
こんなのは?

class Object
 BLACKHOLE = Object.new
 def BLACKHOLE.to_s() "()" end
 def BLACKHOLE.method_missing(*x,&y) self end
 def default(v=BLACKHOLE,&b) self or BLACKHOLE end
 def and() default end
end

class NilClass
 def default(v=BLACKHOLE,&b) block_given? ? yield : v end
end

puts ARGV.shift.and.hex
puts ARGV.shift.default("0").hex