How do I find a comment with PPI and then insert code before it?

Question

I'm trying to find the comment # VERSION in a perl source file. I then want to insert the version before the comment (or in place of doesn't matter). Could anyone tell me the right way to do this with PPI?

before

use strict;
use warnings;
package My::Package;
# VERSION
...

after

use strict;
use warnings;
package My::Package;
our $VERSION = 0.1;# VERSION
...

maintaining the # VERSION in the end result is optional

I actually have a couple of ideas on how to find # VERSION but one is a regex of a serialized ppi doc which doesn't seem right, and the other is using find_first on a Comment but if it's not the first I'm not sure what to do.

Updated code This seems closer to a correct solution since it only looks at the comments. but I'm not sure how to use or really how to create a new variable.

#!/usr/bin/env perl
use 5.012;
use strict;
use warnings;

use PPI;

my $ppi = PPI::Document->new('test.pm');

my $comments = $ppi->find('PPI::Token::Comment');

my $version = PPI::Statement::Variable->new;

foreach ( @{$comments} ) {
    if ( /^\s*#\s+VERSION\b$/ ) {
        $_->replace($version);
    }
}

UPDATE

The answer to this question became the foundation for DZP::OurPkgVersion

Answer 1

Here's some code that does something like what you describe - It'll get you started anyway. It's edited from Catalyst::Helper::AuthDBIC (source), which is a full example of working with PPI (although bits of it may not be best practices):

sub make_model {
    ### snip some stuff
    my $module = "lib/$user_schema_path.pm";
    my $doc = PPI::Document->new($module);
    my $digest_code = # some code
    my $comments = $doc->find(
        sub { $_[1]->isa('PPI::Token::Comment')}
    );
    my $last_comment = $comments->[$#{$comments}];
    $last_comment->set_content($digest_code);
    $doc->save($module);
}

I suppose in your case you grab the $comments arrayref and modify the first item that matches /VERSION/ with the replacement content.

And here's the final code courtesy of the poster:

#!/usr/bin/env perl
use 5.012;
use warnings;

use PPI;

my $ppi = PPI::Document->new('test.pm');

my $comments = $ppi->find('PPI::Token::Comment');

my $version = 0.01;

my $_;
foreach ( @{$comments} ) {
    if ( /^(\s*)(#\s+VERSION\b)$/ ) {
        my $code = "$1" . 'our $VERSION = ' . "$version;$2\n";
        $_->set_content("$code");
    }
}
$ppi->save('test1.pm');