I think sigils in Perl 6 denote variable scope at a glance; so you don't have to write self.X everywhere.
Also you get to know if a variable is only block scope, method scope, class variable, etc.
Also you get to know if a variable is only block scope, method scope, class variable, etc.
Twigils in Perl 6 are where the scope indicators come in, clarifying class instance vars, dynamic scope, and so on.
So if I see %.foo I can tell you that this variable can be used as the Associative role, that it is scoped as an instance variable, and that it has an accessor with the same name.
For more, see the first few sections of http://doc.perl6.org/language/variables