[okdana]

I don't know of any that require it. But it's common to see punctuation characters escaped like that because Perl (and PCRE and its various cousins/descendants) allows you to escape any non-meta-character and have it treated as a literal.

I suppose the two main benefits are

(a) neither the writer nor the reader has to remember which punctuation characters are meta-characters (you just have to remember that it's always a literal if it's escaped), and

(b) in implementations like PHP's which try to replicate the Perl-style 'delimited' syntax (e.g., /foo/), it prevents characters in the pattern from conflicting with the delimiters.

Maybe there's some other advantage but i can't think of what.