in reply to Why would one want in a regex a class with only a single entry?

Negated single character classes are very useful. Often a quick path for ridding oneself of .*. Poor (and lucky; use a parser for real work) man's HTML stripper: s{</?[a-z][^>]*>}{}g;

(sidenote: "pique" ne "peak")

In Section Seekers of Perl Wisdom