Problem Statement

A number wheel has: A number is generated/yielded from a named wheel by: Given the wheel the number 1 is first generated, then 2, then 3, 1, 2, 3, 1, ... Note: When more than one wheel is defined as a set of intersecting wheels then the first named wheel is assumed to be the one that values are generated from. Given the wheels: The series of numbers generated starts: The intersections of number wheels can be more complex, (and might loop forever), and wheels may be multiply connected. Note: If a named wheel is referenced more than once by one or many other wheels, then there is only one position of the wheel that is advanced by each and all references to it. E.g. Generate and show the first twenty terms of the sequence of numbers generated from these groups: Show your output here, on this page.

Let's start with the solution:

use strict;
use warnings;
use feature 'say';

sub get_next {
    my($w,%wheels) = @_;
    my $wh = \@{$wheels{$w}}; # reference, not a copy
    my $value = $$wh[0][$$wh[1]];
    $$wh[1] = ($$wh[1]+1) % @{$$wh[0]};
    defined $wheels{$value} ? get_next($value,%wheels) : $value;
}

sub spin_wheels {
    my(%wheels) = @_;
    say "$_: " . join ', ', @{${$wheels{$_}}[0]} for sort keys %wheels;
    print get_next('A', %wheels) . ' ' for 1..20; print "\n\n";
}

spin_wheels(%$_) for
(
 {'A' => [['1', '2', '3'], 0]},
 {'A' => [['1', 'B', '2'], 0], 'B' => [['3', '4'], 0]},
 {'A' => [['1', 'D', 'D'], 0], 'D' => [['6', '7', '8'], 0]},
 {'A' => [['1', 'B', 'C'], 0], 'B' => [['3', '4'], 0], 'C' => [['5', 'B'], 0]},
);