#!/usr/bin/perl
use strict;
use warnings;

# Shuffle unlimited number of lines from ARGV to STDOUT
# using tempfiles

my $SPREAD    = 50;
my $TERMINATE = 1000;

use File::Temp qw( tempfile );
use IO::File;
use List::Util qw( shuffle );

sub shuffle_lines {
    my ( $infh, $outfh ) = @_;

    my @temp = map { scalar tempfile } 1 .. $SPREAD;
    my @count = (0) x $SPREAD;

    while (<$infh>) {
        my $i = int rand $SPREAD;
        $temp[$i]->print($_);
        $count[$i]++;
    }

    for my $i ( 0 .. $#count ) {
        my $fh = $temp[$i];
        seek $fh, 0, 0;

        if ( $count[$i] <= $TERMINATE ) {
            print $outfh shuffle <$fh>;
        }
        else {
            shuffle_lines( $fh, $outfh );
        }
    }
}

shuffle_lines( \*ARGV, \*STDOUT );