$ perl -E '
    use Data::Dump;

    {
        say "*** Autovivification";

        my $h = { b => {} };
        dd $h;

        my $f = $h->{b}{c};
        say $f // "undefined";
        dd $h;

        my $g = $h->{b}{c}{d};
        say $g // "undefined";
        dd $h;
    }

    {
        say "*** No autovivification";

        my $h = { b => {} };
        dd $h;

        my $f = $h->{b}{c};
        say $f // "undefined";
        dd $h;

        my $g = exists $h->{b}{c} ? $h->{b}{c}{d} : undef;
        say $g // "undefined";
        dd $h;
    }

    {
        say "*** Autovivify then delete";

        my $h = { b => {} };
        dd $h;

        my $f = $h->{b}{c}{x}{y}{z};
        say $f // "undefined";
        dd $h;
        delete $h->{b}{c};
        dd $h;
    }

'