What this does is uses the special token __PACKAGE__ to invoke a static (class) method called compile() with the arguments you see there. Specifically, an array reference with four elements.

The __PACKAGE__ token yields the current package that the interpreter is executing in (this wording is kind of cramped, I realize, but I can't think of a better way to say it right now). If the interpreter encounters it in an inherited method from within a subclass, it will yield that subclasses name. What this means is, a method in an intended base-class can write this as a way of invoking compile as a method, without using an actual object reference. It's still treated as a method invocation, and uses the @ISA search path of the actual (sub)class, not the original class from which it was derived.

--rjray

__PACKAGE__ is defined in perldata.

After you understand that __PACKAGE__ will be replaced with the current package, the workings of the method call are described in perlobj and elsewhere.

To discover this yourself, along with the other references to __PACKAGE__, try:

perldoc -l perl
[download]

UPDATE
Oops. Kanji pointed out that his post did answer the where. But the idea of using grep is still worth knowing about as a way to find these things out when you don't know where to look first.

It runs compile() in the current package. It seems to be a fairly odd/redundant thing to do IMHO, but maybe I'm missing a particular nuance.

Anyhoo, see perlobj's Method Invocation and perldata's Scalar Value Constructors (string literals) for more.

    --k.

In your journal, you mention a DBI book offer. I think you have a lot of good knowledge, but you often seem confused on basic concepts like the one above. I do not think you are ready to write that book. Maybe it is just luck that I happen to know what __PACKAGE__ is for, but you have already encountered it and did not notice. Why do you pose as an expert when you miss things like this?

In your debates with chromatic, you repeatedly misunderstand the points of the argument in question and you have called vroom an asshole. You've compared Perlmonks to a religious cult. How can I take you seriously? When you can convince me that you are worth listening to, I will listen.