Try re-writing this without aliasing and it will either be much less clear syntactically; or vastly less efficient...

BrowserUk operates in an environment in which it is vital to squeeze every last, living computron from any processor, algorithm or function with which he deals, so I am not inclined to dispute his assertion that indirect access is "vastly less efficient".

I would argue with his assertion about clarity. This, of course, is very much a matter of personal taste; I'm not aware of any widely accepted metric for benchmarking 'clarity' – or even for defining its meaning! I would say that the (untested) way I have re-written  mmMxM() below is, to my taste, at least as clear as the original. (Again, all issues of performance are entirely neglected. And I don't understand what this thing is doing in the first place... some kind of matrix multiply?)

use constant N => 3;

sub mmMxM {
    
    my ($ar_A,  # ref. to array of ...
        $ar_B,  # ref. to array of ...
        ) = @_;

    my @c = map [ map 0, 0..N ], 0..N;  # AoA of zeros
    
    for my $i (0..N) {
        for my $j (0..N) {
            $c[$i][$j] += $ar_A->[$i][$_] * $ar_B->[$_][$j] for 0..N;
            }
        }
        
    return \@c;

    }
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I have, believe me, the utmost respect for BrowserUk, a most subtle and puissant (that's puissant, not pissant!) monk whose programming boots I am not fit to lick clean, but I felt compelled to offer my USD0.02 on the subject of clarity.