Dynamic rules syntax for append characters in certain position

[gege]

I want know is there any dynamic syntax for rule-based attack file to append in certain position.
For example, append character before the last character of a word like:
from password to passworRd.
from superman to supermaAn
I know I could use iNX syntax but it is not effective since the length of a word in a wordlist is different each others.
So, is there any kind of syntax for that matter?