sub current_balance {
  my $self = shift;
  if (@_) {
    my $new = shift;
    croak "not a number"
      unless Scalar::Util::looks_like_number($new);
    $self->{current_balance} = $new;
  }
  return $self->{current_balance};
}

##</code><code>##

has current_balance => (is => 'rw', isa => 'Num');

##</code><code>##

package DebuggingDB;
use Moose;
foreach my $method (qw/select insert update delete/)
{
  before $method => sub { warn "$method was called" };
}

##</code><code>##

package DebuggingDB;
use Moose::Role;
foreach my $method (qw/select insert update delete/)
{
  before $method => sub { warn "$method was called" };
}

##</code><code>##

use Moose::Util qw/apply_all_roles/;
apply_all_roles('DB', 'DebuggingDB') if $ENV{DEBUG};

##</code><code>##

my $accounts  = DB->new(...);
my $marketing = DB->new(...);

use Moose::Util qw/apply_all_roles/;
apply_all_roles($marketing, 'DebuggingDB') if $ENV{DEBUG};