Graphics::Potrace
A few months ago I released Graphics::Potrace, that provides Perl bindings to the potrace library. So, if you want to convert rasters into vectors from Perl... you know where to go.
Installation requires that both the potrace command line program and the library (with headers). The potrace program is actually looked for only to check for existence of potrace... but ensure that the library and the headers are there too.
May I suggest putting it on github or a similar service?
@Ben: actually it's already at https://github.com/polettix/Graphics-Potrace - thanks for asking!
May I suggest indicating the github repostitory in your module? For example see this: http://cpansearch.perl.org/src/BKB/JSON-Parse-0.29/Makefile.PL
In particular the META_MERGE does the work here.
I don't know how to do that with Dist::Zilla but I am sure there is a way.
How to convince Meta CPAN to show a link to the version control system of a distribution? for ExtUtils::MakeMaker, Module::Build, Module::Install and Dist::Zilla
Instead of checking for the potrace command, you should use Devel::CheckLib. That's the standard way of verifying availability of an external library dependency.