Most core modules were introduced a long time ago ( antique coding standards) and have to comply to backwards compatibility (hindered further development).

The debugger for instance is sometimes using the main:: namespace and is very hard to maintain.

It would need a major rewrite, but this would most certainly break many products building on top of it.

(actually such incompatibilities introduced by patches happen quite often)

Or take Time::Seconds, changing the constants to objects would certainly break other code expecting plain scalars in edge cases.

now just try to patch and start to argue with P5P...

Keep in mind that many tests are missing since its old code.(sic)

I could link to a talk were a IT guru explains why module authors shouldn't aspire to enter standard library status, b/c they loose all control to apply changes.

Ironically its Guido van Rossum ...

Update: see

minute 49