@echo off & setlocal EnableDelayedExpansion

set While=if "%1" equ "While" ( for /L %%? in () do if
set Do=(
set EndWhile=) else exit ^^!WhileResult^^! ) else cmd /Q /C "%~F0"

if "%1" equ "While" goto %2


rem A Fibonacci While
set /a "x=0","y=1
:WhileBody
%While% !z! leq 500 %do%
   if defined z echo !z!
   set /a "z=x + y", "x=y", "y=z"
%EndWhile% While WhileBody