List manipulations

[Ron]

Greetings

I'm in the proces of moving a project to OS X that  uses a lot of xthings to
manipulate text and lists. These xthings will not be made useable on OS X so
I'm exploring transcripts aternatives. I won't ask for all of them at once
but I will start with a question of columns in hope that it will give me the
information that enables me to solve some of the other problems on my own.
Here goes.

I simply want to add/extract columns of text of an existing list. So with
something like:

a,b,c
d,e,f
g,h,i

I would like to add an item between say item 2 and 3 (as delimited by the
comma) and I would like to extract items 1 and 3 from all the lines.

This is somewhat simplified from what I do but I think it will point me in
the right direction.

Thanks
Ron