Unfortunately, piping STDERR to /dev/null hid the key mistake in this benchmark. You have declared @a and @b as lexical variables, and passed the code snippets to Benchmark as strings. The eval of the code snippets occurs within Benchmark, where the lexical @a and @b are not in scope. Thus, all of the code snippets are iterating over an empty array! The difference in execution time that you saw is just noise.

To avoid this problem, you should either declare @a and @b as global variables or pass the code snippets as anonymous subroutine references.

Here's an improved benchmark: 

#!/usr/bin/perl -w

use 5.006;

use strict;
use Benchmark qw/ cmpthese /;

use vars qw/ @a @b /;

@a = ('a'..'z');

cmpthese(-3, {
   '1' => '@b = map uc,@a',
   '2' => '@b = map uc $_,@a',
   '3' => '@b = map uc(),@a',
   '4' => '@b = map uc($_),@a',
   '5' => '@b = map {uc} @a',
   '6' => '@b = map {uc $_} @a',
   '7' => '@b = map {uc()} @a',
   '8' => '@b = map {uc($_)} @a',
});

__END__

Benchmark: running 1, 2, 3, 4, 5, 6, 7, 8, each for at least 3 CPU sec
+onds...
         1:  4 wallclock secs ( 3.17 usr +  0.01 sys =  3.18 CPU) @ 97
+06.92/s (n=30868)
         2:  4 wallclock secs ( 3.18 usr +  0.02 sys =  3.20 CPU) @ 97
+10.31/s (n=31073)
         3:  4 wallclock secs ( 3.13 usr +  0.02 sys =  3.15 CPU) @ 97
+73.02/s (n=30785)
         4:  4 wallclock secs ( 3.13 usr +  0.01 sys =  3.14 CPU) @ 98
+98.09/s (n=31080)
         5:  3 wallclock secs ( 3.17 usr +  0.00 sys =  3.17 CPU) @ 96
+11.67/s (n=30469)
         6:  3 wallclock secs ( 3.18 usr +  0.01 sys =  3.19 CPU) @ 96
+50.47/s (n=30785)
         7:  4 wallclock secs ( 3.04 usr +  0.02 sys =  3.06 CPU) @ 95
+82.68/s (n=29323)
         8:  4 wallclock secs ( 3.32 usr +  0.01 sys =  3.33 CPU) @ 95
+33.33/s (n=31746)
    Rate   8   7   5   6   1   2   3   4
8 9533/s  -- -1% -1% -1% -2% -2% -2% -4%
7 9583/s  1%  -- -0% -1% -1% -1% -2% -3%
5 9612/s  1%  0%  -- -0% -1% -1% -2% -3%
6 9650/s  1%  1%  0%  -- -1% -1% -1% -3%
1 9707/s  2%  1%  1%  1%  -- -0% -1% -2%
2 9710/s  2%  1%  1%  1%  0%  -- -1% -2%
3 9773/s  3%  2%  2%  1%  1%  1%  -- -1%
4 9898/s  4%  3%  3%  3%  2%  2%  1%  --

[download]
The difference between the solutions is still insignificant. With repeated benchmarks, the order of the solutions will change, and the percentage differences will remain small.

In reply to Re: Re: Tribute to TMTOWTDI by chipmunk
in thread Tribute to TMTOWTDI by s0ttle

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