Further to Fletch's reply:   Please see perlre, perlretut, and perlrequick and perhaps some of these articles. (Note: From Perl version 5.10 onward,  ++ is one of a set of valid regex metacharacter sequences  ?+ *+ ++ {n,m}+ denoting a "possessive" quantifier that does not "give up" anything it may have matched. (Update: But  +++++ is still invalid!))