github/linguist — pull request #161 by BaiGang (2012-05-02 05:10:12+00:00)
Title: Add .pm6 to  Perl extensions for Perl6 

Added .pm6 to Perl extensions.

Conventionally, some Perl6 modules use pm6 as extension to differentiate from the currently common Perl 5 modules. Here are some examples:

+ https://github.com/uasi/messagepack-pm6/blob/master/lib/MessagePack.pm6
+ https://github.com/supernovus/perl6-mime-types/blob/master/lib/MIME/Types.pm6

So I believe adding .pm6 to perl syntax blob sets makes sense.