Question

It seems strange to me that Perl would allow a package to export symbols into another package’s namespace. The exporting package doesn’t know if the using package already defined a symbol by the same name, and it certainly can’t guarantee that it’s the only package exporting a symbol by that name.

A very common problem caused by this is using CGI and LWP::Simple at the same time. Both packages export head() and cause an error. I know, it’s easy enough to work around, but that’s not the point. You shouldn’t have to employ work arounds to use two practically-core Perl libraries.

As far as I can see, the only reason to do this is laziness. You save some key strokes by not typing Foo:: or using an object interface, but is it really worth it?

Answer 1

The practice of exporting all the functions from a module by default is not the recommended one for Perl. You should only export functions if you have a good reason. The recommended practice is to use EXPORT_OK so that the user has to type the name of the required function, like:

use My::Module 'my_function';

Modules from way back when, like LWP::Simple and CGI, were written before this recommendation came in, and it’s hard now to alter them to not export things since it would break existing software. I guess the recommendation came about through people noticing problems like that.

Anyway Perl’s object-oriented objects or whatever it’s called doesn’t require you to export anything, and you don’t not have to say $foo->, so that part of your question is wrong.