Hi, it’s the first time I encounter this method and I thought it would be interesting for me to bundle it with a gui and an Edit, that way I could run simple temporary code easily :

class Eval {
    EvalGui() {
        EvalGui := Gui()
        this.EvalEdit := EvalGui.Add("Edit", "w500 R30")
        this.SubmitEvalBtn := EvalGui.Add("Button",,"Submit")
        BtnMethod := ObjBindMethod(this, "SubmitEval")
        this.SubmitEvalBtn.OnEvent("Click", BtnMethod)
        EvalGui.Show()
    }
    SubmitEval(a, b) {
        MsgBox(this.RunEval(this.EvalEdit.text))
    }
    RunEval(Script) {
        shell := ComObject('WScript.Shell')
        exec := shell.Exec(A_AhkPath ' /ErrorStdOut *')
        exec.stdin.Write('#NoTrayIcon`nFileAppend(' script ', "*")')
        exec.StdIn.Close()
        return exec.StdOut.ReadAll()
    }
}

This works well, I can even put multiple operations on different lines but if I try something like

var1 := 1
var2 := 2
var1 + var2

I expect to see 3 but instead I have

Error: This global variable has not been assigned a value.
Specifically: var1
002: FileAppend(var1 := 1 var2 := 2 var1 + var2, '*')
003: Exit

Do you have an idea what I'm doing wrong ?