Revision 1e440eac-50ad-43f8-acd4-f0e44e9dfb1b - Code Golf Stack Exchange

#Perl, <strike>70</strike> <strike>68</strike> 66 characters

 $"=",";@a=A..M;$i.="{@a}"x++$x." "for@a;map!/(.)1円{3}/&&say,glob$i

Usage:

 $ perl -E 'code' > output_file

I've only been able to test the code with the `A..F` range, but with enough time and resources the same code should be applicable from A to M.

Interestingly, the `<>` form of the `glob` operator refuses to work on my machine, else I could have saved 2 characters.