package My::DB;
use strict;
use DBI;

use vars qw( $dbname );
$dbname = 'dbi:mysql:production_db';

{ my $dbh;

sub dbh {
  $dbh ||= DBI->new($dbname);
  $dbh;
};

  sub disconnect {
    $dbh->disconnect
      if $dbh;
  };
};

package main;
use My::DB;

my $dbh = My::DB::dbh;

# ... do stuff

##</code><code>##

use strict;
use My::DB;
{
  no warnings 'redefine';
  $My::DB::dbname = 'dbi:mysql:test_db';
};

my $dbh = My::DB::dbh;

...

##</code><code>##

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web