Try:

my $dbConnectString = 'dbi:Oracle:' .
  '(LOAD_BALANCE=on)'.
  '(ADDRESS=(PROTOCOL=TCP)(HOST=myhost1)(PORT=1521))'.
  '(ADDRESS=(PROTOCOL=TCP)(HOST=myhost2)(PORT=1521))'.
  '(CONNECT_DATA=(SERVICE_NAME=pcipJDBC.oracle.com))';
[download]

Or, you can put something like

SIMPLE= (DESCRIPTION=
   (LOAD_BALANCE=on)
   (ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)
                          (PORT=1521)
                          (HOST=al4.almg.uucp))
                 (ADDRESS=(PROTOCOL=TCP)
                          (PORT=1521)
                          (HOST=al4.almg.uucp))
   )
   (CONNECT_DATA= (SERVICE_NAME=pcipJDBC.oracle.com))
)
[download]

in your 'tnsnames.ora' file, and use

  my $dbConnectString = 'dbi:Oracle:SIMPLE';
[download]