#!/usr/bin/env perl -l

use strict;
use warnings;

use constant BASE => ord('A') - 1;
use constant MAX  => ord('Z') - BASE;

my @tests = (
    0 .. 3, 24 .. 28, 
    26**2+24 .. 26**2+28,
    26**3+26**2+24 .. 26**3+26**2+28,
);

print "IN: $_ OUT: ", translate($_) for @tests;

sub translate {
    my ($in, $out) = @_;

    $out ||= [];

    return join '', @$out if $in == 0;

    my $mod = $in % MAX || MAX;

    unshift @$out, chr $mod + BASE;

    my $new_in = ($in - $mod) / MAX;

    translate($new_in, $out);
}