package Devel::Stop;
use strict;
use warnings;

sub DB::DB {
  # Execute the code you want to run here
  my $result = main::foo();
  print STDERR "1..2\n";
  print STDERR ((defined $result ? "ok 1" : "not ok 1")," - got a value\n");
  print STDERR (($result eq "I am foo" ? "ok 2" : "not ok 2"), " - right value\n");
  exit(0);
}
1;

##</code><code>##

joe-desk-> perl -d:Stop xxx
1..2
ok 1 - got a value
ok 2 - right value

##</code><code>##

perl -d:Stop monster.pl