I dropped in here because I saw "Sybase", but:

You should probably use @ISA and SUPER when you want to override methods from existing modules. Something like:

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;
}
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If you do it this way the whole system becomes extensible - you'll note that I never mention Sybase::DBlib in the package itself - only in the @ISA - and this lets perl decide at run-time what methods to call based on the inheritance tree.

Michael