That odd-looking regex is matching "rather hot at on " followed by pretty much anything that isn't CPU, and that will work in perl as well (though /rather hot at on (?!CPU)/ would be a more natural way to do it in perl).

Perl regexs are a superset of egrep, and the extensions perl offers use syntax that is illegal as an egrep regex, according to what I see about egrep in SUSv3. (The only possible exception is that, while SUSv3 does allow the {2}, {2,}, and {1,2} quantifiers, it doesn't specify that a ? afterward has any special meaning, as it does in perl.)

In reply to Re: differnce between egrep and perl regex ? by ysth
in thread differnce between egrep and perl regex ? by Random_Walk

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