Corion... Maybe I misunderstand your use of

$DB::single=1
[download]

To use that, doesn't the code needs to be loaded with the debugger?
So every sub is already wrapped with a DB::sub() like Rolf suggests.
and the whole script is already slowed down before I hit the $DB::single =1;

If I don't load through debugger I get:

Name "DB::single" used only once: possible typo at fix_ahdl_dcfx_const
+raint_file.pl line 78.
[download]

I can fix that warning by adding

use DB;
[download]

But I still can't interact with the debugger without running with the perl -d flag.

Now I'm really done spending time on this :)
But it has helped me understand the debugger a bit more.