evil_ruby.rb

class Underscore < BasicObject
  def initialize(invocations = [])
    @invocations = invocations
  end

  def to_proc
    invocations = @invocations
    ::Kernel.lambda do |val|
      invocations.reduce(val) do |val, (name, args, block)|
        val.send(name, *args, &block)
      end
    end
  end

  def respond_to_missing?(*)
    true
  end

  def method_missing(name, *args, &block)
    ::Underscore.new(@invocations + [[name, args, block]])
  end
end

_ = Underscore.new

["foo", "bar", "quox"].map(&_.gsub("oo", "aa")).select(&_.length <= 3) # => ["faa", "bar"]

IIRC underscore or lodash or something has a syntax like myArray.filter(length: 3) Sooo convenient.