concatenation vs interpolation

concatenation.rb

require 'benchmark'

Benchmark.bm do |x|
  x.report("concatenation") do
    for i in 0..30000000 do
      str = "a=" << "10" << ",b=" << "20" << ",c=" << "30" << "."
    end
  end

  x.report("interpolation") do
    for i in 0..30000000 do
      str = "a=#{'10'},b=#{'20'},c=#{'30'}."
    end
  end
end

jruby.txt

-- concatenation --
      user     system      total        real
 11.753000   0.000000  11.753000 ( 11.712000)
-- interpolation --
      user     system      total        real
  1.796000   0.000000   1.796000 (  1.796000)

macruby.txt

-- concatenation --
      user     system      total        real
259.490000   3.960000 263.450000 (170.512197)
-- interpolation --
      user     system      total        real
 31.720000   0.560000  32.280000 ( 19.904950)

ruby-1.8.7.txt

-- concatenation --
      user     system      total        real
 53.250000   0.040000  53.290000 ( 53.310574)
-- interpolation --
      user     system      total        real
  5.150000   0.010000   5.160000 (  5.159601)

ruby-1.9.2-p180.txt

-- concatenation --
      user     system      total        real
 33.560000   0.070000  33.630000 ( 33.625422)
-- interpolation --
      user     system      total        real
  4.390000   0.010000   4.400000 (  4.392276)