Bulk file rename using regular expressions on Windows

@echo off
============ ========================= ===================== =================== =======
rem Copyright: Owen Duffy, 2015. All rights reserved.
rem A batch file for RE based file rename.
rem Uses sed, see http://gnuwin32.sourceforge.net/packages/sed.htm .

rem test for command extensions
if "~x0"=="%~x0" goto EXTERROR 
if "%%~x0"=="%~x0" goto EXTERROR
if not CmdExtVersion 2 goto EXTERROR

rem start
set SED=sed

rem deal with options
if not #%1==#-n goto getsedexpr
set noaction=y
shift
echo Trial run only, rename disabled.

rem get the sedexpr string
:getsedexpr
set sedexpr=%1
shift
if #%sedexpr%==# goto usage

for %%f in (%1 %2 %3 %4 %5 %6 %7 %8 %9) do call :dosed "%%f"
goto cleanup

:dosed
rem extract old filename+ext
for %%f in (%1) do set oldname="%%~nf%%~xf"
rem extract rename arguments
for /f "usebackq tokens=*" %%n in (`echo %oldname% ^| %SED% -r -e %sedexpr%`) do call :doren %1 %%n %oldname%
exit /b

:doren
if %2==%3 exit /b
echo rename %1 %2
if not #%noaction%==#y rename %1 %2
exit /b

:ERREXIST
echo cannot rename %1 as %2% as %2 exists.
exit /b

:usage
echo Usage: srename [-n] sedexpr [filenames]
echo.
echo sedexpr is a sed s/// command using extended RE.
echo Example: srename s/\"(.*)\.(.*)\"/"\2.\1"/ *.*
echo.
goto cleanup

:cleanup
set sedexpr=
set SED=
set noaction=
goto eof

:EXTERROR
echo:This script requires command extensions v2 or later!>&2
verify error 2>NUL
goto eof

:eof