benchmark common unix utilities agaisnt pure Perl

#!/usr/bin/perl

use strict;
use warnings;

use Carp;
use List::Util qw/first/;
use Benchmark;

sub benchmark {
	my $subs = shift;

	my ($k, $sub) = each %$subs;
	my $value = $sub->();
	croak "bad" if first { $value ne $_->() and print "$value\n", $_->(), "\n" } values %$subs;

	Benchmark::cmpthese -1, $subs;
}

benchmark {
	cat   => sub {
		return qx/cat $0/;
	},
	perl => sub {
		open my $fh, "<", $0 or die "$!";
		local $/ = undef;
		return scalar <$fh>;
	},
};

benchmark {
	ls   => sub {
		return join "", map { chomp; $_ } qx/ls/;
	},
	perl => sub {
		return join "", sort glob "*";
	},
};