Follow-on Question: special character in SED routine

Question

ref. http://discussions.apple.com/thread.jspa?threadID=1281065&tstart=0
Camelot successfully answered my specific question in the above thread. When I closed that out, I tacked on a related question -- but either that was missed or there's not a straightforward solution.
The question is: how do I deal with a single quotation mark (') in a routine such as
do shell script "echo " & T & " | sed 's/
" & punct_ & "/X/g'
where punct_ is "'"????
Camelot's solution was for brackets by incorporating an "-E" switch:
do shell script "echo " & T & " | sed -E 's/
" & punct_ & "/X/g'
I found that by also adding an escape:
do shell script "echo " & T & " | sed -E 's/
\\" & punct_ & "/X/g'
it worked for brackets and virtually all other standard punctuation -- but not for the single item "'". Now I'm finding that I really need to be able to deal with "'". Nothing I've tried has worked.

Answer 1

Ahh.
Please try this instead.
--SCRIPT
set rr to {}
repeat with p in "`';:&(){}[]<>\""
set p to p's contents
set t to "one two " & p
if p = "'" then
set sed_ to "sed -E 's/'\\''/X/g'" -- i.e. "sed -E 's/'" & "\\'" & "'/X/g'"
else
set sed_ to "sed -E 's/\\" & p & "/X/g'"
end if
set s_ to "echo " & quoted form of t & " | " & sed_
set end of rr to do shell script s_
end repeat
return rr
--END OF SCRIPT
cf.
sh.1.html
Quoting:
Enclosing characters in single quotes preserves the literal value of
each character within the quotes. A single quote may not occur between
single quotes, even when preceded by a backslash.
Good luck,
Hiroto
PS. Regarding NBSPs in my previous post, which are now not present, it is simply because I had editted my post as such! Sorry for any confusion I may have made.
(The reason I often use   or other HTML numerical entities is to prevent fora software from intrepretting some string as formatting directive.)