Mention importance of closing handles in 5to6

Author: rafaelschipiura

doc/Language/5to6-perlfunc.pod6

@@ -919,6 +919,8 @@ 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 possible to remember to call C<close> at the right time, but the recommended idiom is to write a C<LEAVE> block with the closing intructions right after opening the file.
+
 =head2 opendir
 
 =item opendir DIRHANDLE, EXPR