#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Math::Base::Convert;

my $converter = 'Math::Base::Convert'->new(10, ['A' .. 'Z']);
say $converter->cnv(1000);
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The strings will be a bit different to what you proposed, as A stands for 0 (thus it's A, B, C, ..., Z, BA, BB, BC, etc.), but it's not clear whether it matters.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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