I mean, if Perl 6 didn't want to be confused with being the same language as Perl 5, it didn't have to increment the version number by one and keep the name. As far as why one would want Perl 6 to just be Perl 5 plus some new stuff, that's really how most languages handle keeping the same name and incrementing the version by one. People who have Perl 5 code and want to keep writing in the same language but with more whathaveyou probably want Perl 6 The Completely Separate Language to go away so that Perl can get the kind of Perl 6 any other language would've gotten by now.