You need a separate database handle (dbh) for each connection that is going to a different server. Some DBD drivers require a separate database handle for each connection.

$dbh1 = DBI->connect($DSN,$sqluser,$sqlpass)
    || die "Cannot connect: $DBI::errstr\n" unless $dbh1;
$dbh2 = DBI->connect($DSN2,$sqluser2,$sqlpass2)
    || die "Cannot connect: $DBI::errstr\n" unless $dbh2;
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You would then pass the appropriate db handle to any subroutines:

sub my_query {
  my $my_dbh = shift;
  my $query = shift;

 ....
}

my_query($dbh1, "select * from potatoes");
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