package My::Db;
use Sybase::DBlib;

our @ISA=qw(Sybase::DBlib);

# new() is only needed if you need to do additional
# stuff - otherwise Sybase::DBlib's new() is called 
# automatically
sub new {
    my $package = shift;
    my $dbh = $package::SUPER->new(@_);
    # do something with $dbh here ....

    return $dbh;
}

# Override dbnextrow() to allow ad-hoc processing
sub dbnextrow {
    my $self = shift;

    # Call the real dbnextrow()
    my @row = $self::SUPER->dbnextrow(@_);
    # and now do some magic with @row before
    # returning it...
    ....

    return @row;
}