for %%a in (a123,a465,a789) do (
set b=%%a
set c=%b:a=a被替换%
echo %C%
)
pause

setlocal enabledelayedexpansion
for !!a in (a123,a465,a789) do (set b=!!a
set c=!b:a=a被替换!
echo !C!
)
pause

setlocal enabledelayedexpansion
for %%a in ("a123,a465,a789") do (set b=%%a
	set c=!b:a=a被替换!
	echo !C!
)
pause