dos for 话语嵌套出错

dos for 语句嵌套出错.
@echo off
set yy=%date:~0,4%
set mm=%date:~5,2%
set dd=%date:~8,2%
set /a yy%%=400
if %yy% equ 0 (set rdd=29) else (set rdd=28)
set str=31/%rdd%/31/30/31/30/31/31/30/31/30/31
for /l %%i in (1,1,%mm%) do (
echo %%i
set/a mon=%%i-1
for /f "tokens=%mon% delims=/" %%x in ("%str%") do (
echo %%x
)
)
pause


将蓝色一段放在第一个for里面提示"不应有delims=/"
如果把他放在第一个for外面就不会有问题..
请各位高手帮帮忙,帮小弟看一下,到底是怎么回啊.谢谢了

[解决办法]

BatchFile code

@echo offSETLOCALset yy=%date:~0,4%set mm=%date:~5,2%set dd=%date:~8,2%set /a yy%%=400if %yy% equ 0 (set rdd=29) else (set rdd=28)set str=31/%rdd%/31/30/31/30/31/31/30/31/30/31for /l %%i in (1,1,%mm%) do ( echo %%i call :MON %%i %str%):MONfor /f "tokens=%1 delims=/" %%x in ("%2") do echo %%xgoto :EOF:EOFENDLOCAL