Why do you ask?

So I can frame the question better, and because I can't really think of any other purpose for the hook :)

I think you'll find https://metacpan.org/pod/Plack::Handler::Apache2#STARTUP-FILE interesting, as well as https://metacpan.org/pod/Plack::Component#OBJECT-LIFECYCLE and especially https://metacpan.org/pod/Plack::Builder#INLINE-MIDDLEWARE

So you can create your own init_hook as an anonymous inline Plack::Middleware

builder {
  ...
  enable \&child_init_phase;
  $app;
};
...
sub child_init_phase {
    my( $app ) = @_;
    ...   ## your init stuff here
    $app; ## return app unmodified
}
[download]

Thanks, I had read the Plack::Handler::Apache2 doc but not the others.

I will give this a try, but...it's not clear to me how it is doing anything at child init time, not compile time.

--
A math joke: r = | |csc(θ)|+|sec(θ)| |-| |csc(θ)|-|sec(θ)| |

I will give this a try, but...it's not clear to me how it is doing anything at child init time, not compile time.

now you've confused me :) some more

At what time, other than child init time, would any plackish webserver create an app object of your app and then wait for incoming requests?

That is pretty much "child init time" in terms of PSGI ...

So the app object is created, builder runs the "enable" callback, and then the webserver waits for requests to give to app

Oh yeah, I see , it is no different than just doing it in the constructor :) except maybe slightly semantically different (if its not part of the app, then do nothing middleware seems appropriate)

I think child_init_time is about knowing too much about the webserver

PSGI is about apps, ::Middleware is about wrapping apps (daisy chain), and Plack::Handler is about connecting PSGI apps to webservers (hey random webserver run this app_

I just can't see where child_init_time belongs as a PSGI/Plack concept ...