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(I posted this on my blog to keep up with my Iron Man quota, but since I got no comments there, I decided to re-post it here where I know people enjoy a good Perl puzzle.)

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 lin +e 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 lin +e 1. BEGIN failed--compilation aborted at -e line 1.

-xdg

Code written by xdg and posted on PerlMonks is public domain. It is provided as is with no warranties, express or implied, of any kind. Posted code may not have been tested. Use of posted code is at your own risk.


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