#! perl -slw
use strict;
use Tie::File;
use Benchmark::Timer;

our $N ||= 1000;

sub shuffle {
        my $ref = @_ == 1 ? $_[ 0 ] : [ @_ ];
        for( 0 .. $#$ref ) {
                my $p = $_ + rand( @{ $ref } - $_ );
                @{ $ref }[ $_, $p ] = @{ $ref }[ $p, $_ ];
        }
        return unless defined wantarray;
        return wantarray ? @{ $ref } : $ref;
}

open OUT, '>', 'junk.dat' or die $!;
printf OUT "%030d\n", $_ for 0 .. $N;
close OUT;

my @lines;
tie @lines, 'Tie::File', 'junk.dat';

my $T = new Benchmark::Timer;
$T->start( "shuffle $N" );

shuffle \@lines;

$T->stop( "shuffle $N" );
$T->report;