Kevin's Weblog

Or our if you prefer. Whatever you do, don’t refer to variables in the current package using the full, explicit package name. Concretely, don’t say,

@My::Package::ISA = qw( My::SuperClass );

Instead, write

our @ISA = qw( My::SuperClass );

or

use vars qw( @ISA );
@ISA = qw( My::SuperClass );

The problem with the first is that it is typo-prone. If you typo the package name, perl -cw won’t complain (in fact, perl will happily do exactly what you said), but you’ll get errors like ‘Can’t locate object method “foo” via package “My::Package”’. This is particularly likely to happen when you create a new subclass and copy the old subclass to use as a template. The alternatives are typo-proof, and easier to read to boot.

(BTW, this is a specific case of the general principle Don’t Repeat Yourself. In this case, you already typed the package name once in the package directive. Doing it again anywhere else in the file is just asking for trouble sometime later.)