perl.exe -d pm.919064.4.pl
Default die handler restored.

Loading DB routines from perl5db.pl version 1.07
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(pm.919064.4.pl:4):       print ASDF(19), "\n";
main::(pm.919064.4.pl:5):       BEGIN {
  DB<1> s
main::ASDF(pm.919064.4.pl:9):           my $b = $_[0] + 1;
  DB<1> x $a
0  undef
  DB<2> s
20
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.
  DB<2> q