Revive pull request #1348: "Issue 9882 - Implement a "tee" style InputRange...

...so that a function can be called during a chain of InputRanges."
On Fri, Jul 11, 2014 at 03:25:30AM -0700, Dmitry Olshansky wrote:
[...]
> > +auto tee(Flag!"pipeOnPop" pipeOnPop = Yes.pipeOnPop, R1, R2)(R1 inputRange, R2 outputRange)
> 
> WAT? Flag enum? 
> I recall the decision was to 'set phazers on vaporize' and drop it as
> failed idea before even releasing it. Yet it's in public and
> apparently already in use.
[...]

I use it in my code. What's wrong with it?