I just finished upgrading our large and complex Perl-based internal production system to run under a newer version of Linux which comes with a newer Perl and other newer library versions.
Yes, we face a similar problem across many different Unix flavours. We don't use the system Perl on any platform though, always build our own Perl from C sources. But yes it's a big and hairy problem which is why we're gonna do it early in the release cycle to allow plenty of time for flushing out obscure bugs. Unfortunately, we've got pretty poor test coverage on much of our code, so we'll need to do quite a bit of manual testing.

BTW, I was flabbergasted to hear Titus Winters in C++ as a Live at Head Language claim that Google have a single C++ code repository, shared across the whole company, containing mega millions of lines of code and that they always "Live at Head", meaning that everyone is always using the latest version of all code ... so they never do "upgrades"! As you might expect, to pull this off, you need strong discipline and excellent test coverage, combined with very sophisticated automated tools.

Some points from Titus Winters talk:

Titus Winters is the founder of Abseil and chair for Library Evolution Working Group (design for the C++ standard library).

Update 2023: See also: Re: Rosetta Test: Long List is Long - Abseil

In reply to Re^3: Criteria for when to use a cpan module (Titus Winters Talk) by eyepopslikeamosquito
in thread Criteria for when to use a cpan module by nysus

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