The answer would be because I understand that is what I am supposed to do because Perl uses underscores in the version number to indicate a development release. This release is currently a development release 0.1_1 with an underscore.

Good answer!

I strongly suspect that it was you eyepopslikeamosquito who directed me towards this practice as you were the one who helpfully provided the information I needed to publish my first module

Yes Bod, I believe you are correct.

The version numbers should be boring link you mentioned by David Golden is indeed listed at Software Versioning links ... which is listed at Writing Solid CPAN Modules.

Update: Re: What do I use to release a module to CPAN for the first time? by davido similarly endorses $VERSION = eval $VERSION ... as do the official Perl docs perlmodstyle (in the Version numbering sub-section). Thanks Bod.

I would conclude our code review meeting by reaching for a towel to wipe the egg off my face. :)

I would conclude our code review meeting by reaching for a towel to wipe the egg off my face. :)

...and I would ensure you save face by asking for your expert opinion on what you would do if you were me when this situation recurs...

Which of these do you suggest I use and why? I am not entirely sure of the practical differences.

our $VERSION = '0.1_1';
$VERSION = eval $VERSION;
[download]

or perhaps

our $VERSION = '0.1_1';
$VERSION = eval { $VERSION };
[download]

or maybe

use version;

our $VERSION = version->parse('0.1_1');
[download]

or something else entirely...

I believe that eval { ... }; is compiled just once whereas eval ...; is compiled each time the module is instantiated. This may make a difference if the module is created for each use like MIME::Lite. However, this module should only be created once and subsequent method calls achieve everything it does.

I don't see the point in fetching in the version module (even though it is core) to do something that can be done in two lines of simple code. Perhaps it does something more that I'm not aware of?

The reasonable version of this idiom is:

our $VERSION = '0.1_1';
$VERSION =~ tr/_//d;
[download]

% perl -wle '
  our $VERSION = "0.1_1";
  $VERSION = eval $VERSION;
  if ($VERSION > 0.1 && $VERSION < 0.2) {
    print "ok";
  } else {
    print "not ok";
  }
'
ok

% perl -wle '
  our $VERSION = "0.1_1";
  $VERSION = eval { $VERSION };
  if ($VERSION > 0.1 && $VERSION < 0.2) {
    print "ok";
  } else {
    print "not ok";
  }
'
Argument "0.1_1" isn't numeric in numeric gt (>) at -e line 4.
not ok
%
[download]

eval STRING and eval BLOCK do different things. In this case the BLOCK form is effectively a no-op, so the string is numified using standard coercion during the comparison, and yields the value 0.1 (plus a warning). The string form means "take this string and interpret it as a program" - and Perl code lets us put underscores in numbers, even though the standard coercion rejects them, so it evaluates as the value 0.11.

I don't know about the version->parse variant, but I imagine that PAUSE would not find a version number to parse, so the module would not be indexed correctly.

which is listed at Writing Solid CPAN Modules.

You may want to add a note that Module::Starter adds reference to CPAN Ratings to the POD it generates. But this is now erroneous - see Re^2: CPAN Ratings...

For information, I've found the post I used to create the first module...
Re: What do I use to release a module to CPAN for the first time?

Step 5 covers setting $VERSION and I followed the instructions...