my $my_cnf = 'path_to_somewhere_safe/my_cnf.cnf';

my $dsn =
  "DBI:mysql:;" . 
  "mysql_read_default_file=$my_cnf";

my $dbh = DBI->connect(
    $dsn, 
    undef, 
    undef, 
    {RaiseError => 1}
) or  die "DBI::errstr: $DBI::errstr";

##</code><code>##

# my_cnf.cnf

[client]
host     = hostname
database = my_db
user     = my_usr
password = my_pwd