#! /usr/bin/perl
use strict;
use warnings;
chop $";
my @c = ('0'..'9', 'a'..'z', 'A'..'Z');
sub generate_list {
        for(my @ii = (0) x ($_[0] + 1); $ii[0] == 0; do {
                for(my $i = $#ii; ++$ii[$i] == @c; $ii[$i--] = 0) {}
        } ) {
                print "@c[@ii[1..$#ii]]\n";
        }
}
generate_list 2;