Release 0.81

Perlbrew Release 0.81

perlbrew 0.81 was released at 2017-12-09T15:12:04+0900 with these notable changes:

• Thanks to our contributors: Luca Ferrari, Zac Bentley, perlancar, Nicolas R, gregor herrmann, Paul Cochrane
• New command: clone-modules
• Recognize tarball in .tar.xz extension
• The output of "availables" is now sorted by versions
• Unbreak the integration with cperl releases
• Make perlbrew install runs correctly on AIX
• support the current perl blead (5.28)