Regular expression is not listed in the article, but it blew my mind when I first used it in Perl. Any of sed/awk/perl/python/ruby/javascript could have expose the author to regular expressions, but maybe they didn't find it as transformative as I did.
'' is one of the first special thing that computers made me look at. Even a simple msdos glob .exe felt like a superpower. regexps were the next level but a two edged weapon as everybody knows. That said I never leveraged PCRE extended capabilities.
