Hi fortesque,

In your code it seems like you want the variable $radius_ref to contain a reference to the array @radius. And I understand why you might expect that simply assigning it like my $radius_ref = @radius; might do that for you, and you wouldn't be the only one. Assigning to a scalar variable is one example of what's called scalar context in Perl. And when you have an array in scalar context, like here, what you get is the length of the array (that is, the number of elements in it). So $radius_ref will contain the number of elements in the array @radius.

Whereas \@radius will take a reference to the array, which is what you want.

This is explained in the Arrays section of perlintro, and in more detail in perldata.