G'day fkento,

The short answer is that these represent author errors.

Take a look at perlpod. Near the start you'll see a description of both an "Ordinary Paragraph" and a "Verbatim Paragraph". Note that the former allows formatting codes but the latter does not.

About halfway down that page, you'll find "Formatting Codes". Here you'll see an explanation of "C<code> -- code text", "L<name> -- a hyperlink", and many others.

Now look at the "source code for Net::Amazon::S3::Client", you'll see at both lines 153 and 161:

        # returns a L<Net::Amazon::S3::Client::Bucket> object
[download]

Because those lines, and the lines around them, start with whitespace, they form a verbatim paragraph. Formatting codes are not allowed in verbatim paragraphs, so the "L<...>" is rendered exactly as seen.

I'm not going to go hunting for examples of C<0>. Look in the source code of wherever you saw this: I expect you'll find the same "formatting code within a verbatim paragraph" error.

"When reading documentation on metacpan.org, I frequently see stuff like this:"

I've read a lot of CPAN documentation and I can't remember seeing this in the past (certainly not frequently). I did note that the "Net-Amazon-S3 distribution" has many modules with the same error. I've never used any modules in the Net::Amazon:: namespace, so I don't know how widespread this problem is. I'd be interested to know if you've encountered this issue with other, unrelated modules.