Document %*ENV values are allomorphic
Document %*ENV values are allomorphic

Propspec: https://github.com/perl6/roast/commit/9cf499254
stmuk/doc,tbrowder/doc,tbrowder/doc,perl6/doc,tbrowder/doc,stmuk/doc,stmuk/doc,MasterDuke17/doc,MasterDuke17/doc,perl6/doc,perl6/doc,MasterDuke17/doc,perl6/doc,stmuk/doc,stmuk/doc,MasterDuke17/doc,perl6/doc,tbrowder/doc