Any dzil operation in perl 5.18 or 5.19 starts off with this warning:
Smartmatch is experimental at /Users/ether/.perlbrew/libs/19.0@std/lib/perl5/Dist/Zilla/App/Command/podpreview.pm line 50.
Fixed in https://github.com/pshangov/dist-zilla-app-command-podpreview/pull/1