require_vs_defined.rb

require 'time'

start = Time.now
10000.times do
  require 'time'
end
duration = Time.now - start
printf "require: %f\n", duration

start = Time.now
10000.times do
  defined? ::Time
end
duration = Time.now - start
printf "defined?: %f\n", duration

# ruby require_vs_defined.rb
# require: 1.105543
# defined?: 0.003817