Many moons ago, I implemented a 'say' keyword into the 5.8.something sources and offered it to p5p. Their response was that it needed to be explicitly enabled by the programmer to avoid clashes with existing code that used 'say' as a sub name. So, I implemented that. Their response was, the scoping needs to be lexical, and the mechanism for lexical scoping needs to be generic. I got the NIH message and gave up.

About 5 years later Perl finally got the say keyword with 5.10, and the use feature pragma was the mechanism to enable it's lexical scoping.

To this day, I've never seen anyone, anywhere use use feature qw[ say ]. Everyone who uses say, uses the "use 5.010;" or later global-scope enablement.

Now I've said that out loud, I'm sure that they'll be one or more pedants pop-up claiming they always use use feature qw[ say ]; and all those other things it can optionally enable -- that noone can remember what they are -- explicitly at the closest possible scope in every program and module they write, lording the virtues of clean namespaces...

but can anyone tell me the benefit of getting to the end of a programs run with a clean namespace? Do I win an environmental award or something?