My other "love to hate" oddity of Perl 5 is lvalue subs. To quote me:

As they are, the only thing that can be done with the assigned value is ... well, to assign it to something. Sure, you can decide what to assign it to using the values past via the normal @_ mechanism to make the determination, but there is absolutely no way to inspect the value of the assign value either before you assign it nor after is was assigned. That means it is impossible to perform any verification on the assigned value. This may work for things like substr and splice, that simply don't care what is assigned, but it makes using lvaue subs for any other purpose pretty much useless. I note that vec can and does inspect the value assigned in that it will reject non-numerical assignments as it has to process them in order to use them. This is exactly the facility I would like to use.

I'd really like to see lvalue subs made useful:(