GNU sed version 4.0.5 bug with 2Kb expressions?

[Dr. Richard Botting]

I run a script with some large sed expressions on GNU sed version 3.02 1998
OK.  But on 4.0.5 I get errors like this
sed: -e expression #1, char 4047: Invalid reference \2 on `s' command's RHS

Hacking the expression back to 2kb stopped the error.
I've checked every '\2' and they all have 2 '\(...\)'.

You can see the kind of expression in
        http://www.dick.csci.csusb.edu/dick/tools/mth2html
and I'm blogging my debugging
        http://www.dick.csci.csusb.edu/dick/blog.html

I couldn't a reference in the archives to this feature/bug.
I'm hoping I don't have to slice the sed script up... it will
not be a pleasant activity.

Richard J Botting

Cc: Sys Admin