I am trying to benchmark string concatenation. I am trying to compare string interpolation to string concatenation when they are used to do the same thing. My suspicion is that non-interpolated concatenation beats interpolation, and I have been told that that is true. So I wrote this to test the claim: 

  #! /usr/bin/perl -w
  use strict;
  use Benchmark qw(:all);

  my $sample = 'abcdefghijklmnopqrstuvwxyz';

  sub interpolated ()
  {
    my $s = '';
    for (0 .. 99) {$s = "$s$sample"}
  }

  sub noninterpolated ()
  {
    my $s = '';
    for (0 .. 99) {$s .= $sample}
  }

  cmpthese (-1, {interp => "interpolated()",
                 nonint => "noninterpolated()"});

[download]
Here are the results I get: 
            Rate nonint interp
  nonint 13917/s     --    -0%
  interp 13964/s     0%     --

[download]
Now these results show practically identical numbers, and I believe that they should be more disparate and that my tests are inadequate. So my question is, what can I do to improve my tests? Should I leave the iteration to the cmpthese routine? Am I testing in a way that gets optimized down to identical code?

Thank you all.

In reply to String Concatenation Performance by pbeckingham

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