[BUG] PerlCleanUpHandler seems to execute before reply

PerlCleanUpHandle, that is registered in config executes before reply to the client.
So any time-consuming action in the cleanup handler affects response time without any notion.

This problem can be workarounded by using $ap->pool->cleanup_register(...), that works as expected.

------------------------ details ----------------------

This problem seeems to appear with mod_perl/2.0.9:
ubuntu 14.04: Apache/2.4.7 (Ubuntu) mod_perl/2.0.8 Perl/v5.18.2 -- ok
ubuntu 16.04: Apache/2.4.18 (Ubuntu) mod_perl/2.0.9 Perl/v5.22.1 -- not ok
ubuntu 18.04: Apache/2.4.29 (Ubuntu) mod_perl/2.0.10 Perl/v5.26.1 -- not ok, target
ubuntu 20.04: Apache/2.4.41 (Ubuntu) mod_perl/2.0.11 Perl/v5.30.0 -- not ok

apache.conf:
LoadModule mpm_prefork_module /usr/lib/apache2/modules/mod_mpm_prefork.so
LoadModule perl_module /usr/lib/apache2/modules/mod_perl.so
LoadModule authz_core_module /usr/lib/apache2/modules/mod_authz_core.so
Listen 1080
PidFile /web/.pid
ErrorLog /web/error.log
CustomLog /web/main.log main
ServerName cone2
PerlRequire /web/test.pl
SetHandler perl-script
PerlResponseHandler tnlib::sqcon::handler
PerlCleanUpHandler tnlib::sqcon::cleanuphandler

test.pl:
package tnlib::sqcon;
use strict;
use Apache2::Const qw(OK);
use Apache2::RequestRec ();
use APR::Pool ();
sub handler{
  my($ap)=@_;
  $ap->pool->cleanup_register(sub{ sleep 5; die 5 });
  $ap->status(200);
  return OK;
}
sub cleanuphandler{
  sleep 5;
}
1;

init.pl:
mkdir "/web/root";
system "/usr/sbin/apache2", "-f", "/web/apache.conf";
system "tail -f /web/main.log /web/error.log";

Dockerfile:
FROM ubuntu:18.04
ENV DEBIAN_FRONTEND=noninteractive
RUN apt update && apt install -y netcat-openbsd curl mc libapache2-mod-perl2 libcgi-pm-perl && rm -rf /var/lib/apt/lists/*
RUN useradd --home-dir /web --create-home --user-group --uid 1979 --shell /bin/bash c2
COPY --chown=c2:c2 . /web/
USER c2
CMD ["perl","/web/init.pl"]

docker build -t apache_cleanup .
docker run --init --rm --name apache_cleanup -p '1080:1080' apache_cleanup
time curl localhost:1080/test -v
docker stop apache_cleanup