#! /usr/bin/env perl
use strict; use warnings;
die "usage: $0 <dir>" unless @ARGV == 1;

chdir $ARGV[0] or die "chdir failed: $!";
my @files = grep { not /^(?:\.|\.\.)$/ } readdir '.';
my $i = 0;
for (my $i = 0; @files; $i++) {
  mkdir $i or die "mkdir $i failed: $!";
  for (splice @files, 0, 1000) {
    rename $_, "$i/$_" or die "rename $_ $i/$_ failed: $!";
  }
}