Perl -- Why is 5.16 (not 5.20) the default?

[Michael]

I'd like to know if there is a good reason (such as incompatible language change) for perl to be at 5.16 by default?

I noticed this when I was about to update git -- checking the variants of git, I saw that perl5.16 was the default used by git, and what looks like 2 years out of date.

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