bench.pl

#! /usr/bin/perl
use common::sense;
use Benchmark qw/cmpthese/;

say $^V;

my $datetime = '20101028120000';
cmpthese(1000000, {
    unpack => sub {
        my($year, $month, $day, $hour, $minute, $second) = unpack 'a4a2a2a2a2a2', $datetime;
    },
    regexp => sub {
        my($year, $month, $day, $hour, $minute, $second) = $datetime =~ /^(....)(..)(..)(..)(..)(..)$/;
    },
    substr => sub {
        my $year   = substr $datetime, 0, 4;
        my $month  = substr $datetime, 4, 2;
        my $day    = substr $datetime, 6, 2;
        my $hour   = substr $datetime, 8, 2;
        my $minute = substr $datetime, 10, 2;
        my $second = substr $datetime, 12, 2;
    },
});

__END__

v5.10.0
            Rate regexp unpack substr
regexp  230947/s     --   -53%   -79%
unpack  492611/s   113%     --   -55%
substr 1098901/s   376%   123%     --