# private hash of instances
my %instances;

#...
sub new {
    # ... build up $self, bless it, do whatever
    $instances{$self}=1;
    # ... whatever else you need to do...
}

#...
sub DESTROY {
    # don't double-destroy
    return unless $instances{$self};
    #... do whatever
    $instances{$self}=0;
}

END {
   foreach my $instance(keys %instances) {
       $instance->DESTROY() if $instances{$instance};
   }
}