It actually effectively lost it a bit before. Perl did not invent regular expressions, in fact Larry Wall started with a package by http://en.wikipedia.org/wiki/Henry_Spencer that itself was a reimplementation of an API that appeared in AT&T's V8 Unix that was released in 1985 and was incorporated into standard Unix tools like egrep.
Perl standardized a good enough regular expression dialect that everyone else copied it. But the divergence between "regular expression" and "strictly only regular languages" was already a lost cause.
POSIX regular expressions (file glob patterns, BRE's and ERE's) have more features than regexes in old CS papers, but they are still regular: they compile to automata with no backtracking.
Perl standardized a good enough regular expression dialect that everyone else copied it. But the divergence between "regular expression" and "strictly only regular languages" was already a lost cause.