> perl -d d:/tmp/pm/db_demo.pl 

Loading DB routines from perl5db.pl version 1.57
Editor support enabled.

Enter h or 'h h' for help, or 'perldoc perldebug' for more help.

auto(-2)  DB<1> b testsub
auto(-1)  DB<2> r
outside at d:/tmp/pm/db_demo.pl line 14.
 at d:/tmp/pm/db_demo.pl line 14.
  DB<2> s
inside at d:/tmp/pm/db_demo.pl line 10.
 at d:/tmp/pm/db_demo.pl line 10.
	main::testsub() called at d:/tmp/pm/db_demo.pl line 16
  DB<2>