If it’s going to die anyway then what’s wrong in trying to modernise it and seeing if that does renew interest? Worst case scenario is people don’t migrate and that outcome is no different to if you hadn’t tried. So it feels like the only bad move is not to try at all.
If modernising it splits the community and doesn't suceed, you've redone the Perl6 fiasco, but probably killed both 5 and 7.
Is that better than driving Perl 5 to a stable end? I don't really think so. But I'm not involved in the development of Perl, I'll just keep writing Perl scripts until it gets hard to install.
Perl is going to die if they don’t do anything anyway. So absolute it’s better to risk fragmenting the ecosystem.
If your result for inaction is eventual death anyway, then the sensible thing is to go out swinging. At least that way you have a half chance of reviving the language — which is better than the zero chance you have if you do nothing.