#! perl -slw
use strict;
use Time::HiRes qw[ time ];
use Tie::File;
use Digest::MD5 qw[ md5_hex ];

our $N //= 1e6;

my $start = time;
open OUT, '+>:raw', 'junk.dat';
print OUT md5_hex( 0 );

my $data = 'x'  x 50;
my $md5 = new Digest::MD5;
for ( 1.. $N ) {
    print OUT $data;
    $md5->add( "$data\n" );
}

seek OUT, 0, 0;
print OUT $md5->hexdigest;
close OUT;
printf "Took %.3f seconds\n", time-$start;

$start = time;
tie my @lines, 'Tie::File', 'junk2.dat', memory => 52 * $N;

$md5 = new Digest::MD5;
push @lines, md5_hex( 0 );
for ( 1.. $N ) {
    push @lines, $data;
    $md5->add( "$data\n" );
}

$lines[ 0 ] = $md5->hexdigest;
untie @lines;
printf "Took %.3f seconds\n", time-$start;