#! perl -sw
use 5.010;
use strict;
use Benchmark qw[ cmpthese ];

our $LEN ||= 100;
our $string = 'A' x $LEN;
our @chars = split//, $string;

cmpthese -3, {
    substr => q[
        our $string;
        for (  0 .. length $string ) {
            my $c = substr $string, $_, 1;
        }
    ],
    pre_split => q[
        our @chars;
        for my $c ( @chars ) {
            ;
        }
    ],
    split => q[
        our $string;
        my @chars = split //, $string;
        for my $c ( @chars ) {

        }
    ],
    unpack => q[
        our $string;
        for ( unpack 'C*', $string ) {
            my $c = chr;
        }
    ],
    chop => q[
        our $string;
        my $copy = $string;
        while( my $c = chop $copy ) {
            ;
        }
    ],
    rev_chop => q[
        our $string;
        my $copy = reverse $string;
        while( my $c = chop $copy ) {
            ;
        }
    ],
};

__END__
C:\test>byChar.pl
              Rate     split    unpack    substr  rev_chop      chop pre_split
split      11018/s        --      -74%      -74%      -81%      -82%      -94%
unpack     42513/s      286%        --       -0%      -26%      -30%      -75%
substr     42526/s      286%        0%        --      -26%      -30%      -75%
rev_chop   57794/s      425%       36%       36%        --       -5%      -66%
chop       61056/s      454%       44%       44%        6%        --      -64%
pre_split 171734/s     1459%      304%      304%      197%      181%        --