Can't turn off autocommit

OK, this is more a DBI than a Sybperl question, but anyway, here's my code:

$dbh = DBI->connect("dbi:Sybase:server=$server", $login, $password,
                    {PrintError => 1, AutoCommit => 1});
if (! $dbh) {
    die "Can't connect to $server: $DBI::errstr\n";
}

# do some stuff
.
.
.
$dbh->(AutoCommit) = 0;

When the script hits that autocommit line, I get the message 
"Not a subroutine reference at myscript.pl line 175."

Any ideas?

Thanks,

Steve