I'm delighted of the feedback. Thanks. It's not my main activity but I'm investigating this topic by a while. Now I found some workaround (fixing #line) so that I can have a quite effective remote debugging session. But I'm interested to fix it definitely and understand the problem. Besides starting to add a first question on this site ( here ), I then provided a more detailed question here but I got no solution.

I'm just trying to use 2 old (and I so guess stable-enough) modules, mod_perl and Apache::DB. Even developed by the same author, Doug MacEachern, so I believe they should understand each other. I'm running them out of the box. MY code is only the 4 lines snipped shown, just to see them working as expected for the most simple case.

So the lab is this:

1. have Apache and mod_perl

2. have module Apache::DB

3. use the most simple httpd.conf. Mine is this

4. excute Apache in not-forking mode httpd  -X -DPERLDB -f simple.httpd.conf

5. point your browser to your snippet

6. go to your new fresh debug prompt, arisen magically in the shell of point 4

7. step-step-step-step ... till reaching the sub default_handler of mod_perl

(all will happen inside mod_perl, the file ModPerl::RegistryCooker )

       A) sub default_handler {
          |
       B) |___| $rc = $self->convert_script_to_compiled_handler;
              |       |
              |       |___|  ....
       C)     |           | my $line = $self->get_mark_line;
       D)     |           | my $eval = join '' .....   <------ the joi
+n shown in my opening question above
       E)     |           | $rc = $self->compile(\$eval);
              |           |              |__
              |           |                 | ....
       F)     |           |                 |  eval $$eval;  <----- tr
+anslated in   return $self->error_check;
              |           |                 |
              |           |
       G)     |           | $self->cache_it;
              |
       H)     | $rc = $self->run;
              |              | ....
       I)     |              | eval { $cv->($r, @_) };  ------->   JUM
+P INTO USER CODE  (here #line will not be understood)
[download]

I much appreciate the work of sir MacEachern, as it's a complex matter, but it shouldn't be such a pain to turn them on, after having simplifed your code to 4 lines (shebang, and print CGI header included!, ... so 2 lines). Why that #line is so difficult to understand ? Moreover as already linked (here again) , I found some different opinion on how it should be used so the fixed #line 1 in mod_perl code is on a different choice..... that incidentally does not work so well :)