Why is Regex.match faster with this string in Ruby 2.4?

benchmark.rb

require 'benchmark/ips'
require 'securerandom'

BIG_STRING = <<-EOS
{:event_id=>"c18ae35e83234021bb78d8ba8a8ef2da", :timestamp=>"2016-11-16T23:27:52", :time_spent=>nil, :level=>40, :platform=>"ruby", :sdk=>{"name"=>"sentry-raven", "version"=>"2.1.3"}, :contexts=>{:server_os=>{"name"=>"Darwin", "version"=>"Darwin Kernel Version 16.1.0: Thu Oct 13 21:26:57 PDT 2016; root:xnu-3789.21.3~60/RELEASE_X86_64", "build"=>"16.1.0", "kernel_version"=>"Darwin nodachi.local 16.1.0 Darwin Kernel Version 16.1.0: Thu Oct 13 21:26:57 PDT 2016; root:xnu-3789.21.3~60/RELEASE_X86_64 x86_64"}, :runtime=>{"name"=>"ruby", "version"=>"ruby 2.3.2p217 (2016-11-15 revision 56796) [x86_64-darwin16]"}}, :logger=>"", :culprit=>"benchmarks/benchmark.rb in / at line 10", :server_name=>"nodachi.local", :release=>"425c535", :environment=>"default", :modules=>{"rake"=>"11.3.0", "concurrent-ruby"=>"1.0.2", "i18n"=>"0.7.0", "minitest"=>"5.9.1", "thread_safe"=>"0.3.5", "tzinfo"=>"1.2.2", "activesupport"=>"5.0.0.1", "builder"=>"3.2.2", "erubis"=>"2.7.0", "mini_portile2"=>"2.1.0", "pkg-config"=>"1.1.7", "nokogiri"=>"1.6.8", "rails-dom-testing"=>"2.0.1", "loofah"=>"2.0.3", "rails-html-sanitizer"=>"1.0.3", "actionview"=>"5.0.0.1", "rack"=>"2.0.1", "rack-test"=>"0.6.3", "actionpack"=>"5.0.0.1", "ast"=>"2.3.0", "benchmark-ips"=>"2.5.0", "bundler"=>"1.13.6", "coderay"=>"1.1.1", "connection_pool"=>"2.2.0", "unicode_utils"=>"1.4.0", "coolline"=>"0.5.0", "diff-lcs"=>"1.2.5", "multipart-post"=>"2.0.0", "faraday"=>"0.9.2", "method_source"=>"0.8.2", "parser"=>"2.3.1.4", "power_assert"=>"0.3.1", "powerpack"=>"0.1.1", "slop"=>"3.6.0", "pry"=>"0.10.4", "pry-coolline"=>"0.2.5", "rack-protection"=>"1.5.3", "thor"=>"0.19.1", "railties"=>"5.0.0.1", "rainbow"=>"2.1.0", "redis"=>"3.3.1", "rspec-support"=>"3.5.0", "rspec-core"=>"3.5.4", "rspec-expectations"=>"3.5.0", "rspec-mocks"=>"3.5.0", "rspec"=>"3.5.0", "rspec-rails"=>"3.5.2", "ruby-progressbar"=>"1.8.1", "unicode-display_width"=>"1.1.1", "rubocop"=>"0.41.2", "sentry-raven"=>"2.1.3", "sidekiq"=>"4.2.2", "stackprof"=>"0.2.10", "test-unit"=>"3.2.1", "timecop"=>"0.8.1", "yajl-ruby"=>"1.3.0"}, :extra=>{}, :tags=>{}, :user=>{}, :logentry=>{:params=>nil, :message=>"ZeroDivisionError: divided by 0"}, :exception=>{:values=>[{:type=>"ZeroDivisionError", :value=>"divided by 0", :module=>"", :stacktrace=>{:frames=>[{:pre_context=>["\n", "LOGGER = Logger.new(nil)\n", "\n"], :post_context=>["\n", "Benchmark.ips do |x|\n", "  x.config(:time => 5, :warmup => 2)\n"], :abs_path=>"benchmarks/benchmark.rb", :function=>"<main>", :lineno=>37, :in_app=>false, :context_line=>"puts Raven::Event.from_exception(build_exception).to_hash\n", :project_root=>nil, :filename=>"benchmarks/benchmark.rb"}, {:pre_context=>["#require_relative \"../spec/support/test_rails_app/app\"\n", "\n", "def build_exception\n"], :post_context=>["rescue ZeroDivisionError => exception\n", "  exception\n", "end\n"], :abs_path=>"benchmarks/benchmark.rb", :function=>"build_exception", :lineno=>10, :in_app=>false, :context_line=>"  1 / 0\n", :project_root=>nil, :filename=>"benchmarks/benchmark.rb"}, {:pre_context=>["#require_relative \"../spec/support/test_rails_app/app\"\n", "\n", "def build_exception\n"], :post_context=>["rescue ZeroDivisionError => exception\n", "  exception\n", "end\n"], :abs_path=>"benchmarks/benchmark.rb", :function=>"/", :lineno=>10, :in_app=>false, :context_line=>"  1 / 0\n", :project_root=>nil, :filename=>"benchmarks/benchmark.rb"}]}}]}, :message=>"ZeroDivisionError: divided by 0"}
EOS
CCREGEX = /^(?:\d[ -]*?){13,16}$/

Benchmark.ips do |x|
  x.config(:time => 5, :warmup => 2)

  x.report("match") { CCREGEX.match(BIG_STRING) }
end

ruby-23-results.txt

nodachi:raven-ruby nateberkopec$ ruby benchmarks/regex_benchmark.rb  
Warming up --------------------------------------
               match     4.340k i/100ms
Calculating -------------------------------------
               match     44.996k (± 4.1%) i/s -    225.680k

ruby-24results.txt

ruby benchmarks/regex_benchmark.rb 
Warming up --------------------------------------
               match    12.509k i/100ms
Calculating -------------------------------------
               match    130.241k (± 2.4%) i/s -    662.977k in   5.093459s

2.3.2

Warming up --------------------------------------
               match     3.277k i/100ms
Calculating -------------------------------------
               match     33.784k (± 4.4%) i/s -    170.404k in   5.053575s

2.4.0-preview3

Warming up --------------------------------------
               match     9.505k i/100ms
Calculating -------------------------------------
               match     99.356k (± 3.2%) i/s -    503.765k in   5.075424s