You could make your converter stronger with a couple of fixes.

Regular expressions could be made case insensitive with the i modifier.

More important, if more than one <cpan> element is present in one line, .* will act greedily and gobble more than what you intend to gobble.

For example

<cpan>First::module</cpan> and <cpan>Second::Module</cpan>

will be collapsed into

[cpan://First::Module</cpan> and <cpan>Second::Module]

which is certainly wrong.

You can make * non greedy adding ?:

<cpan>(.*)</cpan> becomes <cpan>(.*?)</cpan>

Other than this, you may want to check Death to Dot Star! for a number of reasons why .* should be avoided when possible.

-- TMTOWTDI