Control Structure: :if / :elseif / :else

:if     (test){arg[.fl]{code}}
:elseif (test){arg[.fl]{code}}
:else         {arg[.fl]{code}}

Commentary Code Result
Commentary 'green' 'yellow' 'red' '???'=>lights;
:for(lights[.light]){13#asc =>nl;
  :if(light='green'){
    light":cruise"nl}
  :elseif(light='yellow'){
    light":floor it"nl}
  :elseif(light='red'){
    light":slam on brakes!!!"nl}
  :else{
    light":what light???"nl}}$;
Result:
green:cruise
yellow:floor it
red:slam on brakes!!!
???:what light???