Cool.subst-mutate only mutates if there's a match
Cool.subst-mutate only mutates if there's a match

So the original Cool object remains unaltered if there was no match.  Which
is probably better for many reasons.  lucasb++ for spotting/suggesting.

labster/rakudo,rakudo/rakudo,tbrowder/rakudo,salortiz/rakudo,softmoth/rakudo,softmoth/rakudo,salortiz/rakudo,rakudo/rakudo,tony-o/rakudo,salortiz/rakudo,softmoth/rakudo,nbrown/rakudo,rakudo/rakudo,salortiz/rakudo,nbrown/rakudo,lucasbuchala/rakudo,tony-o/rakudo,salortiz/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,nbrown/rakudo,Gnouc/rakudo,tbrowder/rakudo,tbrowder/rakudo,rakudo/rakudo,salortiz/rakudo,Gnouc/rakudo,rakudo/rakudo,lucasbuchala/rakudo,tony-o/rakudo,lucasbuchala/rakudo,nbrown/rakudo,tony-o/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,labster/rakudo,lucasbuchala/rakudo,rakudo/rakudo,tbrowder/rakudo,labster/rakudo,labster/rakudo,labster/rakudo,nbrown/rakudo,tony-o/rakudo,MasterDuke17/rakudo,nbrown/rakudo,tbrowder/rakudo,labster/rakudo,Gnouc/rakudo,Gnouc/rakudo,softmoth/rakudo,MasterDuke17/rakudo,lucasbuchala/rakudo,softmoth/rakudo,tony-o/rakudo,MasterDuke17/rakudo