What does this 'flexibily' buy anyone? It's just more complexity for no gain.

Yes - it's just flexibility for the sake of flexibility. All it can ever "buy" is more headaches - and they're easily picked up for free, anyway.

Math::GSL actually does this, btw - which is how I came to notice it. Since Math::GSL contains nearly 50 modules, I have nearly 50 dll's (all from Math::GSL) in perl/site/lib. For perl/site/lib/Math/GSL/Vector.pm, I have perl/site/lib/Vector.dll, etc. As you've noted, that's ok .... so long as no other module (eg Bit::Vector) decides to do the same thing.

I'll write a patch and send it to the Math::GSL authors. It's messy having nearly 50 dll's in perl/site/lib alongside various pm and pod files.

Cheers,
Rob