%h = (
      a => [3, 9, 4],
      b => [2, 1, 3],
      c => [9, 7, 2],
      ...
   )

##</code><code>##

    my ($x,$y,$z) = @{$h{$key}}; 
    $o->{m}[$x][$y][$z] = ...

##</code><code>##

    sub matrixGet {
        my ($o, $x, $y, $z) = @_;
        return $o->{m}[$x][$y][$z];
    }
    sub matrixSet {
        my ($o, $x, $y, $z, $val) = @_;
        $o->{m}[$x][$y][$z] = $val;
    }
    ...
    $o->matrixGet(@{$h{$key}});
    $o->matrixSet(@{$h{$key}},5);

##</code><code>##

    sub matrixGet {
        my ($m, $x, $y, $z) = @_;
        return $m->[$x][$y][$z];
    }
    ...
    matrixGet($o->{m},@{$h{$key}});