my %dbs;
$dbs{$sid_0} = DBI->connect("dbi::$driver0", $user0, $pass0) ||
  die "failed to establish connection to $sid_0 : $DBI::errstr\n";

$dbs{$sid_1} = DBI->connect("dbi::$driver", $user1, $pass1) ||
  die "failed to establish connection to $sid_1 : $DBI::errstr\n";
...
$sth_0 = $dbs{$sid_0}->prepare...
$sth_1 = $dbs{$sid_1}->prepare...