... makes me think maybe we used to trust the cached value

I think https://www.nntp.perl.org/group/perl.perl5.porters/2016/10/msg240576.html and responses is relevant here.
As also mentioned there, the stringification of the NV is retained if the NV is an inf or nan.
I assumed this was ok because stringifications of inf and nan were not affected by locale. (But I notice that stringification of 0.0 to "0" is not retained.)

Cheers,
Rob

In reply to Re^3: Any reason NV is not marked as POK when accessed as string? by syphilis
in thread Any reason NV is not marked as POK when accessed as string? by vr

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