In lieu of Perl 5.x and Perl 6.x I think converting to a code-name branding would help achieve what you seek. Certainly version numbers would be present, but the public face would be the code-name similar to Android OS versions [1].
Perl Camel anyone?
[1] http://en.wikipedia.org/wiki/Android(operatingsystem)#UsageshareofAndroidversions
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