Change to a link to the close routine.

Author: rafaelschipiura

doc/Language/5to6-perlfunc.pod6

@@ -919,7 +919,7 @@ only, read-write, and append, you would use C<:w>, C<:rw>, and C<:a>
 respectively. There are also options for encoding and how the filehandle
 deals with newlines. Details L<here|/routine/open>.
 
-Another important change is that filehandles don't get automatically closed on scope exit. It's necessary to call C<close> explicitly.
+Another important change is that filehandles don't get automatically closed on scope exit. It's necessary to call L<close> explicitly.
 
 =head2 opendir