What's the general rule for naming modules with that extra 'x' in the namespace?

rudder has asked for the wisdom of the Perl Monks concerning the following question:

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Re: What's the general rule for naming modules with that extra 'x' in the namespace? by kyle (Abbot) on Mar 25, 2008 at 18:50 UTC
I believe these are extensions. For example, DBI says extensions should go in DBIx. Moose says the same about MooseX.	[reply]
Re: What's the general rule for naming modules with that extra 'x' in the namespace? by moritz (Cardinal) on Mar 25, 2008 at 19:48 UTC
The 'X' stands for "eXtension", so FooX::Bar is an extension to Foo named Bar. Example: DBIx::Class extends DBI to have class functionality. So just add an X to the thing you want to extend.	[reply]
Re^2: What's the general rule for naming modules with that extra 'x' in the namespace? by rudder (Scribe) on Mar 25, 2008 at 22:26 UTC
Thanks kyle and moritz, but, a class "Foo::Bar::Baz" might inherit from (er... extend) a class "Foo::Bar". So, it looks like if you're dealing with the object oriented, inheritance kind of "extend", you just name your module as shown in the previous paragraph. But if the extending isn't the OO kind, I guess that's where you start using the 'x'.	[reply]
Re^3: What's the general rule for naming modules with that extra 'x' in the namespace? by Anonymous Monk on Mar 26, 2008 at 16:15 UTC
No, this is not the reason. It does not have anything to do with object orientation or whatnot mechanism. We have DBIx and MooseX because timb and stvn own the namespaces without x, and extension module authors are careful not to trample in them. See the module-authors list for further detail.	[reply]