:indexof [%1 - string ; %2 - find index of ; %3 - if defined will store the result in variable with same name]

@echo off

setlocal enableDelayedExpansion

set "str=%~1"

set "s=!str:%~2=&rem.!"

set s=#%s%

if "%s%" equ "#%~1" endlocal& if "%~3" neq "" (set %~3=-1&exit /b 0) else (echo -1&exit /b 0)

set "len=0"

for %%A in (2187 729 243 81 27 9 3 1) do (

set /A mod=2*%%A

for %%Z in (!mod!) do (

if "!s:~%%Z,1!" neq "" (

set /a "len+=%%Z"

set "s=!s:~%%Z!"

) else (

if "!s:~%%A,1!" neq "" (

set /a "len+=%%A"

set "s=!s:~%%A!"

)

)

)

)

endlocal & if "%~3" neq "" (set %~3=%len%) else echo %len%

exit /b 0