"helpful" is quite a stretch. The message produced is just as unhelpful and
uninformative as the source code line. As was demonstrated, one or both
of them gave the recipient not the slightest clue that "//" wouldn't work.
So, "use 5.010;" didn't actually help. At most it just induced surprise
which was worked around in the obvious manner. Hard to expect otherwise.
All "use 5.010;" does is add a layer to obscure the real problem that people
will actually end up dealing with (though, it often just adds a problem layer
when there isn't even a problem underneath).
I had proposed ways to drastically improve how helpful it could be. More
importantly, those would drastically reduce how often it would be pointlessly
obstructive. Unfortunately, the lastest bizarre magic tied to such constructs
makes the feature impossible to improve in an any meaningful way.