"hard quote", "tick"
'' in a bare string literal does minimal interpolation like q//
'' when used with a quote introducer like q, qq, qw is just a generic quote
'' chunks multiple gliphs into a single literal as well as escaping metacharacters.
'' around a method name in a call refers to the prefix operator in method postfix form
' can be used as a symbol in an identifier
' as a namespace separator as in perl5 is always done with :: in perl6