How could I change the array reference to each field value?

As I understand it, the array reference already references each field's value. You need to pass these values to V(). Maybe something like (untested):

sub vector {
    my ($aa) = @_;
    return V(@$aa);
    }
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Again, I haven't studied the relevant module.

As you can see, most of the function defined above is irrelevant. Why not just (also untested):

my $some_scalar = V(@$original_array_reference);
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instead?

Update: After actually looking at Math::Vector::Real, it seems that  V() returns a blessed reference of some kind (update: you also reference | make note of this below), not a floating point number as implied by the  %f format specifier in the OPed  printf statement. You will have to manipulate this  V object into some form of data usable to you, which I cannot judge.