The author mentions that ack "allows you to use Perl-compatible regular expressions (PCRE)" in contrast to grep. I want to point out that grep does too, or at

The author mentions that ack "allows you to use Perl-compatible regular expressions (PCRE)" in contrast to grep. I want to point out that grep does too, or at least the versions on Linux and Mac OS X, when the -E flag is used. I don't know if it actually uses the PCRE library or if it even uses the same character class shortcuts that Perl does, but it's at least modern in the sense that it uses (...) instead of \(...\) for grouping and {n,m} instead of \{n,m\} for specifying the number or range of occurrences, as well as + for {1,}, etc. Edit: Slight fact correction. The author of this article led me to believe that ack uses Perl Compatible Regular Expressions, which is a C library that implements a regular expressions system whose pattern syntax is very similar to what's found in Perl. Now that I've read ack's website, I see that ack is written in Perl and actually uses Perl's regexps. The author must have just meant that ack's regular expressions are literally "Perl-compatible."