Adds example for input

Since there are differences between Python 2 and 3, I just use here
the most similar to Perl 6, which is Python 3 (and say so). Adds
examples for usage in Python and Perl 6. Also reanchors. Refs #2355

doc/Language/py-nutshell.pod6

@@ -728,11 +728,21 @@ run on entering or leaving a block.
         say 'world';
     }
 
-=head2 Input
-X<|raw_input (Python)>
 X<|input (Python)>
+=head2 Input
+
+In Python 3, the C<input> keyword is used to prompt the user:
+
+=begin code :lang<python>
+entered = input("Say hi → ")
+print(entered)
+=end code
+
+When prompted, you can enter C<Hi> or any other string, which will be stored in
+the C<entered> variable. This is similar to L<prompt> in Perl 6:
 
-See the L<prompt> function.
+    my $entered = prompt(" Say hi → ");
+    say $entered # OUTPUT: whatever you entered.
 
 =end pod