Your last six methods could be consolidated:

no strict 'refs';
foreach my $axis ('i', 'j', 'k') {
    *{ $axis } = sub {
        my $self = shift;
        if (@_) {
            $self->{"_$axis"} = shift;
        }
        return $self->{"_$axis"};
    }
}
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If you're willing to limit this to Perl 5.6 and newer, you could also look into lvaluable subroutines. Class::Accessor also handles much of the same thing for you nearly automagically.