benchmark_with_block.rb

def benchmark
  # Mark current time
  start_time = Time.now()
  # Run long callback / yield command
  yield
  # Mark end time
  end_time = Time.now()

  # Calculate total time using marked times
  total_time = end_time - start_time
end

# Be careful, pasting this into IRB will take a long time to print.
# It's a loooong string. :)
long_string = "apple" * 100000000

running_time = benchmark { long_string.reverse }

puts "string.reverse took #{running_time} seconds to run"