Re: lowercase letters for binaries

[Charles Levert]

* On Sunday 2005-11-06 at 22:48:30 +0100, Andreas Schwab wrote:
> Note that POSIX does not allow back-references in EREs,

You're right.  I didn't notice that because
GNU grep does support them (from GNU regex).


> only in BREs which don't have alternation.

Is that the justification?  Strictly speaking,
yes, '([xy])z\1' can always be replaced by
'xzx|yzy', but with more complicated cases,
back-references can seriously cut down the
complexity of a regular expression.