I have been attempting to do some optimization which involved array assignment and iteration. While doing so I found something that confused me but was ultimately unrelated to my production code, as it only occurs when I print some debug.

I have boiled down a loss of almost an order of magnitude to the below test case. I have removed all the test code save for copying an array into another array from my for loop.

I have commented out three different lines of code which I tested one at a time and got a time interval value for. Running with the #<nothing> line, i.e., with no extra line, I see similar performance to the line say @array. What has me confused is the performance I get after printing an interpolated copy of the array with the line say "@array".

If anyone can enlighten me, even if I am missing something elementary, it would be greatly appreciated.

use Time::HiRes qw(gettimeofday tv_interval);

my @array = (1..100);
# say "@array"; # 0.332776 s
# say @array;   # 0.052496 s
# #<nothing>    # 0.052361 s

my $t0 = [gettimeofday];

for (1..10000)
{
   my @array2 = @array;
}

say tv_interval($t0);

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In reply to Strange performance loss after interpolating an array and then copying to another array; by Kc12349

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