Generate a sequence of unique characters e.g. 3333, 3334 ... YYYX, YYYY

generate_unique_sequence_chars.pl

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

my $chars_str = '3456789ABCDEFGHJKMNPRSTUVWXY';
my @chars = split //, $chars_str;

               # a  b  c  d
my $template = [ 0, 0, 0, 0, 0 ];
my $dead_end = 0;

while (1) {
    print join('', map { $chars[$_] } @$template),"\n";

    my $ti = scalar(@$template)-1;

    if ($template->[$ti] < scalar(@chars)-1) {
        $template->[$ti]++;
    }
    else {
        while (1) {
            $ti--;
            if ($template->[$ti] < scalar(@chars)-1) {
                $template->[$ti]++;
                for ($ti+1 .. scalar(@$template)-1) {
                    $template->[$_] = 0;
                }
                last;
            }
            if ($ti < 0) {
                $dead_end = 1;
                last;
            }
        }
    }

    last if ($dead_end);
}

1;