#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw(cmpthese);

my $x = "0123456789abcdefg" x 6000 . "XXX";

sub subst   { my $s = $x; $s =~ s/(.{16})/$1 /sg; $s };
sub up      { join ' ', unpack '(A16)*', $x };
sub re      { join ' ', $x=~ /(.{1,16})/g };
sub m_substr {
    my $s = $x;
    for (my $i=16*int((length($s)-1)/16);$i;$i-=16) { 
       substr($s,$i,0)=" "; 
    }
    $s;
}

sub readline {
    local $/ = \16;
    my $s;
    open my $handle, '<', \$x;
    $s = <$handle>;
    while (<$handle>) {
        $s .= ' ' . $_;
    }
    $s;
}

my $ref = subst();

sub wrap {
    my ($impl, $sub) = @_;
    die "Wrong result for $impl!" unless $sub->() eq $ref;
}

cmpthese(-1, {
    subst   => wrap('subst', \&subst),
    re      => wrap('re', \&re),
    unpack  => wrap('unpack',\&up),
    substr  => wrap('substr',\&m_substr),
    readl   => wrap('readline', \&readline),
})
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