gistfile1.rb

require 'rubyperf'
m = Perf::Meter.new

result2=m.measure(:bang) do
    10000000.times do
        "asdf".sub!(/a/, "")
    end
end
result1=m.measure(:non_bang) do
    10000000.times do
        "asdf".sub(/a/, "")
    end
end

puts m.report_simple

# measure        : percent%   accuracy  count       user     system      total        real
# \blocks        : 100.000%  excellent      2  14.660000   0.000000  14.660000 ( 14.658286)
#     \bang      :  46.239%  excellent      1   6.780000   0.000000   6.780000 (  6.776532)
#     \non_bang  :  53.761%  excellent      1   7.880000   0.000000   7.880000 (  7.881754)