opMixin or mixin function templates with convenience operator?

[Bastiaan Veelo]

On Thursday, 12 December 2019 at 10:33:21 UTC, aliak wrote:
> So the interpolated dip thread got me thinking, and wondering 
> if any time there's been a proposal for an opMixin? It can 
> possibly be the hash tag symbol? And opMixin does what mixin 
> does, and mixes the code in the spot.

Maybe (ab)use opDollar?

> auto html = json$q{ // compile error if invalid json
>   "hello": "${variable}",
>   "another: "${a + b}",
> };