debugging mod_perl fails

My setup's versions:
Ubuntu Server 17.04
Apache2 2.4.25
Perl 5.24.1
mod_perl 2.10
Apache::DB 0.14
 
I precisely followed the manual from this site:
     http://plosquare.blogspot.de/2009/04/debugging-modperl-applications-with.html
and used a simple .pl-page to test debugging mod_perl.
 
I tried all kinds of tweaks (e.g. tried to set a breakpoint on the page with $DB::single = 1;)
and changes (e.g. tried a common mod_perl handler instead of a ModPerl::Registry-managed .pl-file) but no matter what I tried:
the DB console correctly showed up when I called the .pl-page
but it was never usable because it never stopped at a code line.
The page's execution seemed to already have completed
(which was also visible in the browser).
Output:
  root@DEVELOP:/etc/apache2/sites-available# apache2ctl -k start -X -DPERLDB
   [notice] Apache::DB initialized in child 7194
   Loading DB routines from perl5db.pl version 1.49_05 
   Editor support available.
   Enter h or 'h h' for help, or 'man perldebug' for more help.
 
I also tried “apache2ctl -k start -DPERLDB -DNO_DETACH -DONE_PROCESS“. Same result as with “-X“.
Is it not working because apache2 must be compiled/configured in
a certain way so that the debugger can stop at a certain code line?
Did someone get debugging using Apache::DB to work with an up-to-date
apache2 (>=2.4) and mod_perl (2.10) versions or is it only feasible with
older versions because maybe Apache::DB can't cope with newer mod_perl
or apache2 versions anymore?
 
I would greatly appreciate any help!