At least Perl had admitted it.
Dealing with Python after mostly taking a pause around time 3.0 was introduced, I was shocked at the mess. And unlike with Perl 6, which took quite a clean break even before it decided to rebrand, you ended up with situation where both were around semi-equally, and there were "fun" bugs introduced in Python 3 that caused explosive bugs that we couldn't figure out in beginning because things would always work on developer machines...
Perl strikes me as the only major language which failed a transition though. I mean where the actual developers of a language developed a new version, released as an official new version of the language, and then the entire community stayed behind on the old version to the degree that the new version was renamed and made into its own separate project. Can you think of any other example?
Survivorship bias. Python just barely survived the transition, and you only still use it now because it did make it. Take a look at Perl 6 to see a major language that failed.