$DB1 = "dbi:Sybase:server=server_name;database=db";
use DBI;
 
#
# Open the connection to the database
#
  if ( ! defined( $dbh ) ) {
    $dbh = DBI->connect( $DB1, 'uid', 'passw', 'Sybase' );
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Well, the definition of DBI::connect indicates that the (optional) fourth parameter is a reference to an attributes hash, not a string constant.

If I had to hazard a guess, I'd change your connect to $dbh = DBI->connect( $DB1, 'uid', 'passw' );