package Camel;
use strict;
# Warning, do not use this constructor at home kids.
# It's ugly and will scare the neighbours.
sub new {
  bless {};
}
sub DESTROY {
  print "My camel has sadly passed away.\n";
  }
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use strict;
use Camel;
{
  my $jimmy=Camel->new();
}
#$jimmy is now out of scope and will be DESTROYed.
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CU
Robartes-

I find that it is best, when you free() a pointer, to also set the pointer to NULL. So have your DESTROY method croak if the pointer is already NULL. Then your test script can call DESTROY by hand and then let the object go out of scope and trap the error:

    my $fail= eval {
        {
            my $obj= My::Mod->new();
            $obj->DESTROY();
        }
        1
    };
    print "not "
        unless $fail  &&  $@ =~ /destroyed NULL/;
    print "ok 19\n";
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I hope that eval traps XS-based croak().

And, of course, this won't work in Perl 6 if it doesn't implement reference counting.

DESTROY() is just another method. You can mock it to make sure it's called when you think it should be called, and you can call it with a mock object to make sure it does what you think it should do. The only real trick is knowing that it's called during an end of lifetime cleanup.