DOS Batch: how to parse command line in DOS batch file?

@echo off
REM parse arguments in the format key=value
REM Example codename=g26 action=new lang=en:chs

SETLOCAL
SET CMDLINE=%*
SET CODENAME=
SET ACTION=
SET LANG=
SET BADARGS=
SET VALIDATION=
GOTO main

:SplitArgs
  REM recursive procedure to split off the first two tokens from the input
  echo SplitArgs(%*)
  if "%*" NEQ "" (
    REM %%i = KEY, %%j = VALUE, %%k = remainder of input
    REM delimiters are space character and equals character
    for /F "tokens=1,2,* delims== " %%i in ("%*") do call :AssignKeyValue %%i %%j & call :SplitArgs %%k
  )
  goto :eof

:AssignKeyValue
  REM KEY %1, VALUE %2
  echo   AssignKeyValue(%1, %2)
  if /i %1 EQU codename (
    SET CODENAME=%2
  ) else if /i %1 EQU action (
    SET ACTION=%2
  ) else if /i %1 EQU lang (
    SET LANG=%2
  ) else (
    REM Append unrecognised [key,value] to BADARGS
    echo Unknown KEY %1
    SET BADARGS=%BADARGS%[%1, %2]
  )
  goto :eof

:Validate
 REM VALIDATION == SUCCESS|FAIL
 echo Validating
 SET VALIDATION=FAIL
 if defined CODENAME (
   echo   codename ok
   if defined ACTION (
     echo   action ok
     if defined LANG (
       echo   lang ok
       if defined BADARGS (
         echo   badargs found
       ) ELSE (
         SET VALIDATION=SUCCESS
       )
     )
   )
 )
 goto :eof

:main
  cls
  echo command line is %CMDLINE%
  call :SplitArgs %CMDLINE%
  call :Validate
  if "%VALIDATION%" EQU "SUCCESS" (
    echo **************
    echo Et voila
    echo perl make.pl %CODENAME% %ACTION% %LANG%
    echo **************
  ) else (
    echo Missing or unrecognised tokens in the command line
    echo %BADARGS%
  )

pause

command line is codename=g26 action=new lang=en:chs
SplitArgs(codename=g26 action=new lang=en:chs)
  AssignKeyValue(codename, g26)
SplitArgs(action=new lang=en:chs)
  AssignKeyValue(action, new)
SplitArgs(lang=en:chs)
  AssignKeyValue(lang, en:chs)
SplitArgs()
Validating
  codename ok
  action ok
  lang ok
**************
et voila
perl make.pl g26 new en:chs
**************
Press any key to continue . . .