To add to the above comment, realitve to your question: it all depends on the situation of your application of when you want to use base or @ISA. I have always tried to use base when creating my class hierarchy, however I have also ran into circumstances where I had to use the @ISA array.

Either solution should work in most cases, though I usually also tell people to try use base first.

In either curcumstance, if you are to use the @ISA array, I always put it within a BEGIN block. Maybe for personal preference, although it makes sence to ensure the push happens at compile time, rather than run time.

package MyObject;

use strict;
use warnings;

use vars qw( @ISA );

BEGIN {
  push( @ISA, 'BaseObject' );
};

sub new {
 # Code here
}

# Follow up with some methods

1;
[download]

So, hopefully you can see what I mean here.

Good luck!