So, if you want modifiable scalar parameters, you can change them inside a sub by using $_[0], $_1 etc. as lvalues without resorting to references. Interesting.

Hehe, I have another word for it. I discovered this a couple of months ago and was really blown away because it means that even if you explicitly pass by value, there's no guarantee that your data won't be altered.

Now despite a natural inclination toward "const correctness" (by which I mean maintaining control over what happens to one's data even when passing it by reference to other folk's functions), I've come to live with Perl's motto that you should keep people out of the living room by asking rather than by wielding a shotgun. But this seems like putting the TV right out in the front lawn. So, my question is why is this allowed? Is this a remnant from Perl 4? Will it be maintained in Perl 6?