do global interpolation

[Shuraken007]

I wanted to hide zero value "0 B/s", conditions are supported.

readonly show_speed="#{?#{!=:#{download_speed},0 B/s},#{download_speed},}"

Problem is, that do_interpolation() expands only first #{download_speed}

Please do global variable expanding
result=${input//$download_interpolation/$download_speed}
vs
result=${input/$download_interpolation/$download_speed}