TIMTOWDI :>)
In principle, the application have to know, which connection it wants to use. My recently used solution is, __briefly__:

#configuration
my $conf = "
  <MyConfPool>
    <connection id="firstconn">
      ...DSN credentials
    </connection>
    <connection id="secondconn">
      ...DSN credentials
    </connection>
  </MyConfPool>";

#create object holding connections
use MyConnPool;
my $conn_pool = MyConnPool->new(conf=>$conf);

...

#use some connection
my $conn1 = $conn_pool->get("firstconn");
$conn1->Sql(...);
my $conn2 = $conn_pool->get("secondconn");
$conn2->Sql(...);
[download]

The goal is to implement whole maintenance of connections in that slightly described module, other parts of application will just use it, not carrying if connection is already opened e.t.c.