Playing with ruby's ability to replace keywords.

case.rb

class Ca
  def initialize(obj)
    @obj = obj
    @steps = []
  end

  def wen(*conditions)
    @steps << Proc.new if conditions.any?{|condition| condition === @obj}
  end

  def default
    @steps << Proc.new
  end

  def result
    @steps.first.call
  end

  class << self
    def se(obj, &block)
      kase = self.new(obj)
      kase.instance_eval(&block)
      kase.result
    end
  end
end

#Example usage
["", :a, 1000000000000000000000, 1, {}, []].each do |obj|
  Ca.se obj do
    wen String, Symbol do
      puts "stringish"
    end

    wen Bignum, Integer do
      puts "numericalish"
    end

    default do
      puts "otherish"
    end
  end
end