# Pastebin rDyS5XeS
role StrictClass {
   method TWEAK(*%pars) {
      if %pars.keys (-) self.^attributes>>.name>>.substr(2) -> %error { die "unexpected %error.keys().join(", ")" }
      nextsame
   }
}
say class :: does StrictClass { has $.a }.new: :1a, :2b