You can get the desired behaviour as follows. Set perldb.ini as follows (in the current dir):

C:\>type perldb.ini
$ENV{PERLDB_OPTS}="NonStop frame=2";
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Because perl5db.pl (the debugger in X:\\Perl\lib\perl5db.pl on Win32) is Unix centric it will refuse to read this file due to permissions being too open. A quick patch is to skip the is_safe_file() test on Win32 circa line 317 with something like:

    unless (is_safe_file($file) or $^O =~ m/Win32/ ) {
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There are other options to set the NonStop feature (ie .perldb and set PERLDB_OPTS env var) but that was the only one that worked (after the patch) on Win32 and I was too lazy to debug the debugger any deeper. Anyway here is an example that happily flips into and out of the interactive debugger:

C:\>type test.pl
print "Hello\n";
print "World!\n";
assert( 1 == 0 );
print "In interactive Debugger!\n";
$a = "Still in debugger!\n";
print $a;
assert( 1 == 1 );
print "Escaped Debugger!\n";
print "Still Free!\n";
assert( 0 );
print "Debugger again!\n";

sub assert { $DB::single = $_[0] ? 0 : 1 }

C:\>perl test.pl
Hello
World!
In interactive Debugger!
Still in debugger!
Escaped Debugger!
Still Free!
Debugger again!

C:\>perl -d test.pl
Default die handler restored.
Package test.pl.
Hello
World!
entering main::assert
exited main::assert
4:      print "In interactive Debugger!\n";
  DB<1> n
In interactive Debugger!
5:      $a = "Still in debugger!\n";
  DB<1> n
6:      print $a;
  DB<1> n
Still in debugger!
7:      assert( 1 == 1 );
  DB<1> c
entering main::assert
exited main::assert
Escaped Debugger!
Still Free!
entering main::assert
exited main::assert
11:     print "Debugger again!\n";
  DB<1> c
Debugger again!
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<1> q

C:\>
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