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

# create source numbers if they don't exist
my $many = 500000;
my $source='numbers.csv';
open CSV, '>', $source or die "can't write to $source: $!\n";
for (1..$many) {
    my @numbers;
    push @numbers, (int rand 1000) for (1..5);
    print CSV join ",",@numbers;
    print CSV $/;
}