How do I perform string operations on variables in a for loop?

Question

This sounds dumb, but I can\'t get it to work. I think i just dont\' understand the difference between %%v, %v% and %v

Here\'s what I\'m trying to do:

Answer 1

For people who found this thread looking for how to actually perform string operations on for-loop variables (uses delayed expansion):

setlocal enabledelayedexpansion

...

::Replace "12345" with "abcde"
for %%i in (*.txt) do (
    set temp=%%i
    echo !temp:12345=abcde!
)