Roflscale your xml_http_request? calls by not casting them to booleans

xmlhttp_predicate_speed.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'benchmark/ips'

class ExampleRequest
  def initialize
    @env = {'HTTP_X_REQUESTED_WITH' => 'XMLHttpRequest'}
  end

  def xml_http_request?
    !(@env['HTTP_X_REQUESTED_WITH'] !~ /XMLHttpRequest/i)
  end

  def roflscale_xml_http_request?
    @env['HTTP_X_REQUESTED_WITH'] =~ /XMLHttpRequest/i
  end
end

request = ExampleRequest.new

Benchmark.ips do |ips|
  ips.report("understandable") { request.xml_http_request? }
  ips.report("roflscale")      { request.roflscale_xml_http_request? }
end