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:\>