Originally Posted by RudiC

The entire logic and structure of that script seems suboptimal. For every file found, you (re)open "alter.txt", read every single line, invoke awk twice and - I'm guessing based on your other threads - run something like sed to do the replacements.

Depending on the found files' count this IS going to be lengthy.

I'm not talking of improving the innermost loop here - although there is quite some potential.
Why don't you leave the looping to one single instance of e.g. awk?
Create a list of all file candidates (find can have several paths as starting points) and run awk, first reading all the search/replacement pairs, and then working those on all files presented.