map! vs map

require 'benchmark'

TIMES = 500
Benchmark.bm { |p|
  p.report("new") do
    TIMES.times do
      Dir[(`pwd`).chomp + '/**/*.rb'].map! { |e| e }.sort!
    end
  end
  p.report("old") do
    TIMES.times do
      names = Dir[(`pwd`).chomp + '/**/*.rb'].map { |e| e }
      names.sort!
    end
  end
};


      user     system      total        real
new  0.330000   1.010000   2.510000 (  2.747355)
old  0.350000   1.030000   2.580000 (  2.809858)