in reply to Brief OO question

Not in my opinion, but I rarely do it. My main considerations for doing so are maintainability and performance. If it's a trivial method called often, I'll definitely consider using $_[0] instead of assigning $self first, like your example.

If it's a method that does considerable or complicated things to "$self", or isn't called very often, then I consider $self more maintainable and will prefer it.