Oracle: ORA-24327 need explicit attach before authenticating a user in perl script

Hi,

i write the sequent script:

#######################################################################
use DBI;

my $orachehost = "*********";
my $oracleuser = "**********";
my $orachepasswd = "******";
my $oraclesid = "*****";
my $oracle_home = "/usr/lib/oracle/11.2/client";

$ENV{ORACLE_HOME}=$oracle_home;
$ENV{ORACLE_SID}=$oraclesid;
$ENV{PATH}="$oracle_home/bin";

my $dbh = DBI->connect( "dbi:Oracle:host=$orachehost:sid=$oraclesid",
$oracleuser, $orachepasswd, { AutoCommit =>
1,RaiseError=>1,PrintError=>1 }  ) ||   die("Errore nella connessione
al db: $DBI::errstr");

$dbh->disconnect;

exit 0;

#######################################################################

When i run the script, it doesn't work and write:

DBI connect('host=**********:sid=*******','********',...) failed:
ORA-24327: need explicit attach before authenticating a user (DBD
ERROR: OCISessionBegin) at /usr/local/sbin/myscript.pl

Any ideas?