Document Str.substr(Range)

Author: hoelzro

lib/Type/Str.pod

@@ -440,10 +440,13 @@ object representing the successful match, or C<Any> otherwise.
 =head2 routine substr
 
     multi sub    substr(Str:D $s, Int:D $from, Int:D $chars = $s.chars - $from) returns Str:D
+    multi sub    substr(Str:D $s, Range $from-to) returns Str:D
     multi method substr(Str:D $s: Int:D $from, Int:D $chars = $s.chars - $from) returns Str:D
+    multi method substr(Str:D $s: Range $from-to) returns Str:D
 
 Returns a part of the string, starting from the character with index C<$from>
-(where the first character has index 0) and with length C<$chars>.
+(where the first character has index 0) and with length C<$chars>.  If a range is
+specified, its first and last indices are used to determine the size of the substring.
 
 Examples: