#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw 'cmpthese';

our @dates = qw [092205 092305 092605];
our (@mb, @me, @fb, @fe);

cmpthese(-1, {  
    map_block => '@mb = @dates; map {s{(\d{2})(\d{2})(\d{2})}{$1/$2/$3}} @mb',
    map_expr  => '@me = @dates; map  s{(\d{2})(\d{2})(\d{2})}{$1/$2/$3}, @me',
    for_block => '@fb = @dates; for (@fb) {s{(\d{2})(\d{2})(\d{2})}{$1/$2/$3}}',
    for_expr  => '@fe = @dates; s{(\d{2})(\d{2})(\d{2})}{$1/$2/$3} for @fe',
});

die unless "@mb" eq "@me" && "@mb" eq "@fb" && "@mb" eq "@fe";

__END__
             Rate for_block  for_expr map_block  map_expr
for_block 43115/s        --       -1%       -2%       -6%
for_expr  43530/s        1%        --       -1%       -5%
map_block 43840/s        2%        1%        --       -5%
map_expr  45948/s        7%        6%        5%        --

##</code><code>##

             Rate map_block  for_expr for_block  map_expr
map_block 43050/s        --       -1%       -5%       -7%
for_expr  43631/s        1%        --       -4%       -6%
for_block 45271/s        5%        4%        --       -2%
map_expr  46419/s        8%        6%        3%        --

             Rate  for_expr for_block map_block  map_expr
for_expr  42309/s        --       -3%       -5%       -7%
for_block 43530/s        3%        --       -3%       -5%
map_block 44660/s        6%        3%        --       -2%
map_expr  45583/s        8%        5%        2%        --

             Rate for_block  for_expr map_block  map_expr
for_block 43115/s        --       -1%       -3%       -7%
for_expr  43530/s        1%        --       -2%       -6%
map_block 44246/s        3%        2%        --       -5%
map_expr  46419/s        8%        7%        5%        --

##</code><code>##

pack => '@pk = @dates; @pk = map {join "/", unpack "A2 A2 A2", $_} @pk'

##</code><code>##

             Rate  for_expr for_block map_block  map_expr      pack
for_expr  42309/s        --       -0%       -2%       -9%      -48%
for_block 42309/s       -0%        --       -2%       -9%      -48%
map_block 43115/s        2%        2%        --       -7%      -47%
map_expr  46394/s       10%       10%        8%        --      -43%
pack      80736/s       91%       91%       87%       74%        --