Mine was implementing negative lookaround assertions with plain grep -E. I did it for detecting cross-posts between certain newsgroups. The precise regex I used was anchored to the beginning of the line:

^([^e]|e([^s]|s([^\.]|\.([^c]|c([^o]|o([^m]|m([^p]|p([^\.]|\.([^o]|o([^s]|s([^\.]|\.([^l]|l([^i]|i([^n]|n([^u]|u[^x])))))))))))))))

I even made some pseudo-algorithm for building more:

^
([^e]|e
([^s]|s
([^\.]|\.
([^c]|c

<blah>

([^n]|n
([^u]|u
[^x]
)))))))))))))))

[download]

But didn't bother to automate it. In fact, I've never used this again.

--
David Serrano

In reply to Re: The craziest RegExes you ever created by Hue-Bond
in thread The craziest RegExes you ever created by Ieronim

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