Shared via Pony Playground (https://playground.ponylang.io/?gist=9f5507fbea04face1da21459f460166b)

main.pony

use "collections"

actor Main
	new create(env: Env) =>
	  let arr = get_array()
    for n in arr.values() do
      env.out.print(n.string())
    end

	fun get_array(): Array[USize] val =>
	  var arr: (Array[USize] trn | None) = None
	  
	  for i in Range(0, 10) do
	    if i > 2 then
        match consume arr
	      | let arr': Array[USize] trn =>
	        arr'.push(i)
	        arr = consume arr'
  	    else
	        let arr': Array[USize] trn = Array[USize]
	        arr'.push(i)
	        arr = consume arr'
  	    end
	    end
	  end

    match arr
    | let arr': Array[USize] trn =>
      consume arr
    else
      []
    end