The $separator argument to .join isn't constrained to Str.

Author: pmichaud

lib/List.pod

@@ -83,8 +83,8 @@ Returns
 
 =head3  join
 
-    multi sub    join(Str:D $separator, *@list) returns Str:D
-    multi method join(List:D: Str:D $separator) returns Str:D
+    multi sub    join($separator, *@list) returns Str:D
+    multi method join(List:D: $separator) returns Str:D
 
 Treats the elements of the list as strings, interleaves them with
 C<$separator> and concatenates everything into a single string.