clarify section "routine chop" and expand acc. to roast S32-str/chop.t

Author: schultzdavid

doc/Type/Str.rakudoc

@@ -14,16 +14,20 @@ L<immutable|/language/faq#If_Str_is_immutable,_how_does_s///_work?_If_Int_is_imm
 =head2 routine chop
 
      multi method chop(Str:D:)
-     multi method chop(Str:D: Int() $chopping)
+     multi method chop(Str:D: Int() $n)
 
-Returns the string with C<$chopping> characters removed from the end.
+Returns the string with C<$n> characters removed from the end.
+The original string is left unchanged.
+The C<$n> positional is converted to L<C<Int>|/type/Int>
+beforehand.
 
     say "Whateverable".chop(3.6);  # OUTPUT: «Whatevera␤»
     my $string= "Whateverable";
     say $string.chop("3");         # OUTPUT: «Whatevera␤»
 
-The C<$chopping> positional is converted to L<C<Int>|/type/Int> before being applied to the
-string.
+Calls without an argument remove just one character.
+If the string contains fewer characters than are to be chopped,
+the result is the empty string.
 
 =head2 routine chomp