I assume you mean Perl 5 vs Perl 6 ? One could argue that that is exactly what happened in 2008, when the "sister language" meme was introduced. At that time,

I assume you mean Perl 5 vs Perl 6 ? One could argue that that is exactly what happened in 2008, when the "sister language" meme was introduced. At that time, the Perl Porters basically abandoned all support for Perl 6 and started developing on Perl 5 again. So development of Perl 6 basically fell back on just a handful of people, on the Parrot backend, which became less and less acceptable for Perl 6. And then people still wonder why it took so long?