Programming :: RHES 5 - Making Sed Snippet To Be Portable

I have an odd issue that I am running into. My objective is to insert the following lines at the end of /etc/inputrc on an RHES box:

Code:
# alternate mappings for "page up" and "page down" to search the history
"e[5~": history-search-backward
"e[6~": history-search-forward

I would like this sed snippet to be portable and thus far it's worked. However, I ran into one box where after I ran the snippet, Subsequent sessions lost the ability to use the letter "e". The original version I was using looked like this:

Code:
mv /etc/inputrc /tmp/inputrc.orig
sed 's/'$endif'/
# alternate mappings for "page up" and "page down" to search the history
"e[5~": history-search-backward
"e[6~": history-search-forward
&/' /tmp/inputrc.orig > /etc/inputrc

Then instead of using s/ I thought perhaps i/ would be better so I re-did it as:

Code:
mv /etc/inputrc /tmp/inputrc.orig
sed '/'$endif'/ {
i
i
# alternate mappings for "page up" and "page down" to search the history
i
"e[5~": history-search-backward
i
"e[6~": history-search-forward
}' /tmp/inputrc.orig > /etc/inputrc

Both of these produce the expected result BUT they both resulted in the loss of the letter "e". As I mentioned earlier in the post, this was working on 'newer' RHES 5 and up but I have the misfortune of having to support some older RHES 4 boxes in a closed lab. This particular box is an RHES 4u6.