Charles Levert wrote:
[...]
Hence, my question was: is that the
justification used by the POSIX committee when
they standardized on this behavior for EREs?
No. See the Open Group's rationale:
http://www.opengroup.org/onlinepubs/009695399/xrat/xbd_chap09.html#tag_01_09_04
"It was suggested that, in addition to interval expressions, back-references (
'\n' ) should also be added to EREs. This was rejected by the standard
developers as likely to decrease consensus."
Presumably the lack of historical support for back-refs in ERE made it too
controversial.
- Julian
