[Foreigner]

Acuna, можно:

Код:

:: mybatch %var% "key1=1;key2=2;key3=3"

@echo off
setlocal

echo %1
set str="%~2"

for %%i in (%str:;=","%) do 1>nul set %%i

for /f "tokens=1,2 delims==" %%i in ('set key') do echo %%i %%j

Вывод:

Код:

test
key1 1
key2 2
key3 3