If you think of a language as merely a bag of syntax, than Perl 5 and Perl 6 are very different. (You can make the same argument about a lot of versions of a lot of languages.)
If you think of a language as a design philosophy expressed in semantics and syntax -- and a guide to choosing to make the corresponding tradeoffs -- then the "The syntax is very different, thus it's a different language!" argument doesn't work.
Various implementations of Lisps and Schemes are recognizable as Lisps and Schemes for a reason.
If you think of a language as a design philosophy expressed in semantics and syntax -- and a guide to choosing to make the corresponding tradeoffs -- then the "The syntax is very different, thus it's a different language!" argument doesn't work.
Various implementations of Lisps and Schemes are recognizable as Lisps and Schemes for a reason.