Fun with perl

Want to help me out? Run the following code:

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dump qw( ddx );
BEGIN { ddx "DIE=", $SIG{__DIE__}; };
use Test::More tests => 1;
BEGIN { ddx "DIE=", $SIG{__DIE__}; };

diag "Perl: ", sprintf "%vd", $^V;
diag "Test::More: $Test::More::VERSION";
pass "one test";

What do you expect $SIG{__DIE__} to contain? Acceptable answers are undef, "" and "DEFAULT". And the answer varies according to what version of perl and what version of Test::More you are running.

Example output:

# DIE=""
1..1
# DIE=sub { "???" }
# Perl: 5.004_05
# Test::More: 0.47
ok 1 - one test

# die:7: ("DIE=", undef)
1..1
# die:9: ("DIE=", "")
# Perl: 5.8.8
# Test::More: 1.001002
ok 1 - one test

# die:7: ("DIE=", undef)
1..1
# die:9: ("DIE=", undef)
# Perl: 5.10.1
# Test::More: 1.001002
ok 1 - one test

1..1
# -:9: ("DIE=", undef)
# Perl: 5.16.2
# Test::More: 1.001002
ok 1 - one test

And yes, I know 5.004 dates from the previous century.