If I understand right, all they are doing is changing the per-script, per-module defaults to enable current language features, instead of having most features since about 2005 disabled by default.
Perl5 has a very strong position on backward compatibility. Even when they change behaviour or add new syntax, that's disabled by default unless a script or module explicitly asks for the new behaviour.
Each significant feature can be switched off or on per module. Even if the main program turns on features, they remain off for the modules used by the main program.
So as far as I can tell, the proposal is just to change this default, so that modern Perl5 features are available to new code by default, instead of having to be explicitly requested, and there's no radical change or incompatibility planned for v7.
That's a change of compatibility-first culture. It means scripts which don't specify what they do and don't want will indeed break with newer versions, occasionally. However Perl5 changes quite slowly, and it's unusual for something new to break something old anyway.
But it should be easy for scripts to specify what they want.
If there's a "no v7" directive that should be enough at the start of any script or module that wants to keep working while being insulated from future changes. That's not much different, in practice, than what they already have to do to ask for features they do use.
Another idea would be to have two search path directories, with different defaults in each, and modules install into the appropriate one according to module metadata. This would allow existing, old modules to carry on working in v7.
Perl5 has a very strong position on backward compatibility. Even when they change behaviour or add new syntax, that's disabled by default unless a script or module explicitly asks for the new behaviour.
Each significant feature can be switched off or on per module. Even if the main program turns on features, they remain off for the modules used by the main program.
So as far as I can tell, the proposal is just to change this default, so that modern Perl5 features are available to new code by default, instead of having to be explicitly requested, and there's no radical change or incompatibility planned for v7.
That's a change of compatibility-first culture. It means scripts which don't specify what they do and don't want will indeed break with newer versions, occasionally. However Perl5 changes quite slowly, and it's unusual for something new to break something old anyway.
But it should be easy for scripts to specify what they want.
If there's a "no v7" directive that should be enough at the start of any script or module that wants to keep working while being insulated from future changes. That's not much different, in practice, than what they already have to do to ask for features they do use.
Another idea would be to have two search path directories, with different defaults in each, and modules install into the appropriate one according to module metadata. This would allow existing, old modules to carry on working in v7.