#!/usr/bin/perl -w 
use Digest::MD5 qw(md5_hex);
use Time::HiRes qw(gettimeofday tv_interval);

my $howmany = shift || 100;

my $t0;

$t0 = [ gettimeofday ];
for (1..$howmany) { system("md5sum", $0) }
print STDERR tv_interval($t0), "\n";

$t0 = [ gettimeofday ];
for (1..$howmany) {
    open(my $SELF, $0) or die $!;
    local $/ = undef;
    my $buf = <$SELF>;
    close $SELF;
    print md5_hex($buf), "\n";
}
print STDERR tv_interval($t0), "\n";