I’m working on a longer article about version numbers in Perl, why there are now so many ways to screw them up, and some recommendations. In the meantime, I realized that some of my examples for that article might be a fun puzzle for others with some curiosity and time to kill.
Format 🔗︎
Each puzzle consists of the output of several Perl one-liners using different versions of Perl. They are run in a directory with a single file, Foo.pm, like this:
package Foo; use strict; use warnings; our $VERSION = 1.23; 1;
In each puzzle, line 4 (the $VERSION line) is different and the puzzle is to figure out the $VERSION line given only the sample output.
Puzzle 1 🔗︎
$ perl5.10.0 -e 'use Foo 0.001001' $ perl5.8.9 -e 'use Foo 0.001001' Foo version 0.001001 required--this is only version 0.001001 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl5.8.9 -Mversion -e 'use Foo 0.001001'
Puzzle 2 🔗︎
N.B. This puzzle intentionally requests a higher version number than is in Foo.
$ perl5.10.0 -e 'use Foo v0.1_1' Foo version v0.1_1 required--this is only version v0.0_1 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl5.8.0 -e 'use Foo v0.1_1' Foo version v0.1.1 required--this is only version v0.0.1 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl5.6.2 -e 'use Foo v0.1_1' Foo version 0.011 required--this is only version 0 at -e line 1. BEGIN failed--compilation aborted at -e line 1.
Puzzle 3 🔗︎
$ perl5.10.0 -e 'use Foo 0.000001' Foo version 0.000001 required--this is only version v0.0_1 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl5.10.0 -e 'use Foo v0.0_1' $ perl5.8.9 -e 'use Foo v0.0_1' $ perl5.8.0 -e 'use Foo v0.0_1' Foo version v0.0.1 required--this is only version v0.0_1 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl5.6.2 -e 'use Foo v0.0_1' Foo version 0.001 required--this is only version v0.0_1 at -e line 1. BEGIN failed--compilation aborted at -e line 1.
Puzzle 4 🔗︎
$ perl5.10.0 -e 'use Foo v0.1.1' $ perl5.8.9 -e 'use Foo v0.1.1' $ perl5.10.0 -e 'use Foo v0.2.1' Foo version v0.2.1 required--this is only version v0.1.1 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl5.8.9 -e 'use Foo v0.2.1' Foo version 0.002001 required--this is only version 0.001001 at -e line 1. BEGIN failed--compilation aborted at -e line 1.