I know what it does, I know when I would use it, but I honestly can't remember when I've actually utilized a prototype, yet I continue to put the 'ref($proto) || $proto' stuff in my code (I think I may have actually used it once but I'm not sure). In a code review with a 'perl master' (not merlyn) at the conference I pointed out that I'm not sure if its all that useful but he assured me that it was fine. I figure that it has become such an idiomatic perl thing that if you don't do it that way, you take the chance of disappointing someone down the line who might want to utilize it (yeah, it's a weak excuse).

merlyn: I consider any use of this ref($proto) || $proto in new to be "cargo cult programming", and mark it off as such in the code reviews I do.

Hah! beat ya to it. Though I continue to use it, I mark myself off first (and this is what I had in the 'code review'):

sub new {
    # Do the cargo cult OO construction thing
    my $proto = shift;
    my $class = ref($proto) || $proto;
...
[download]