Are you using Perl 5.6 in production?

Perl5 • 5.6 Sun 26 July 2015

There's been quite a bit of discussion this week about Perl 5.6, and how much effort people should put into their ensuring their CPAN distributions work with 5.6. The question I haven't seen asked: is anyone still using 5.6 in production?

Perl 5.6 was released in 2000, and it was a major step forward in a number of ways: Unicode support, the warnings pragma, lvaluable subs, weak references, POSIX character classes and more.

The whole "5.6 support discussion" was apparently started by one of MIYAGAWA's tweets:

"if uploading a module to CPAN means a commitment to support 5.6 i would have never uploaded one"

Following discussions on IRC, twitter and elsewhere, Matt Trout wrote up his thoughts. In response, David Golden wrote up why you shouldn't waste your time on Perl 5.6. Bálint Szilakszi then argued that we should stop supporting 5.6 for security reasons.

MSTROUT and CHROMATIC subsequently had a discussion in reddit comments, which clarified a number of things.

I remembered that MIYAGAWA's cpanm tool keeps track of the versions of Perl seen. I wondered whether that sees any Perl 5.6 users, but Miyagawa-san pointed out that cpanm doesn't support 5.6. He did provide a month's worth of data, which I summarised by major version:

Even numbers are stable releases, the odd numbers are development releases, which is why you don't see much activity for the older development releases (curious that there are any for 5.13.x, 5.15.x, and 5.17.x!)

Notice that the most popular version (amongst cpanm users, remember) is 5.18.x, but the second most popular version is 5.10.x; Perl 5.10.0 was released in December 2007.

Here's that data as a pie chart:

Just over 3% of the requests are from Perl 5.8. I wondered how many of those are smokers and toolchain developers, as opposed to "real-life users of 5.8", but Miyagawa-san told me that the cpanm stats already exclude smokers, CI, etc, as much as possible.

In an interesting P5P post 2 years ago, RIBASUSHI pointed out that although the cpanm userbase is skewed towards early adopters, they're running old versions of Perl. From which I think he's saying that we can assume there are more people out there running very old versions of Perl than we might think.