You could try using Tie::File with a Fisher-Yates shuffle in place:

#!perl
use strict;
use warnings;

use Tie::File;

my $filename = shift;

die 'No file' unless $filename;

my $tie = tie my @file, 'Tie::File', $filename, memory => 20_000_000;
die "Couldn't tie $filename: $!" unless $tie;

$tie->defer();

shuffle(\@file);

$tie->flush();

undef $tie;

untie @file;

sub shuffle {
    my $deck = shift;  # $deck is a reference to an array
    my $i = @$deck;
    while (--$i) {
        my $j = int rand ($i+1);
        @$deck[$i,$j] = @$deck[$j,$i];
    }
}
__END__

[download]

This worked well enough for me using a simple text file containing 1 million lines of random numbers.

In reply to Re: mem usage by kejohm
in thread mem usage by halfcountplus

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.