Well, I've always used this method:

sub db_connect
{
    my (
        $db,    # database to connect to
        $dsn,   # data source name
        );

    # Create data source string and connect ...
    $dsn = "DBI:mysql:".
           "database=".$cfg::params{'DB_NAME'}.";".
           "host=".$cfg::params{'DB_HOST'}.";".
           "port=".$cfg::params{'DB_PORT'};
    $cfg::dbh = DBI->connect( $dsn, $cfg::params{'DB_USER'},
                                $cfg::params{'DB_PASSWD'},
                                {RaiseError => 0, AutoCommit => 1} );

    if( $DBI::errstr)
    {
        exit_with_error($DBI::errstr);
    }
}
[download]

where the $cfg::params are read from a text cfg file, and I've never had a prob with it not working, on many systems.

HTH
Cheers
Chris