Return with weirder exit status of 15 on read error

app/main.go

@@ -23,7 +23,7 @@ func repl(ctx *core.Context) {
 		input, err := getInput(ctx)
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "Error reading input: ", err)
-			os.Exit(1)
+			os.Exit(15)
 		}
 
 		runnable, err := runnable.Parse(ctx, input)