Perl6::Junction => Syntax::Keyword::Junction

Same thing -- essentially, AFAICT -- except that we don't get 'smartmatch
operator is experimental' warnings in 5.18 :)
.pod -> .mkdn
v0.020

	* Drop Perl6::Junction in favor of Syntax::Keyword::Junction Same
	  thing -- essentially, AFAICT -- except that we don't get 'smartmatch
	  operator is experimental' warnings in 5.18 :)