Refactor: convert to nCr and bag().
Refactor: convert to nCr and bag().

perl6/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,perl6/perl6-examples,perl6/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples