fix syntax highlighter handling of =cut

perl terminates pod sections with a =cut directive, but is very loose
about how it parses it. Update the syntax highlighter regex to match how
perl handles this. It doesn't match the pod spec, but this is primarily
doing highlighting on perl code, not pod.

root/static/js/brush-perl.js

@@ -95,7 +95,7 @@ function Brush() {
 
         // don't capture the newline after =cut so that =cut\n\n=head1 will start a new pod section
         {
-            regex: /(^|\n)=\w[\s\S]*?(\n=cut\s*(?=\n)|$)/g,
+            regex: /(^|\n)=\w[\s\S]*?(\n=cut(?![a-zA-Z]).*)/g,
             css: 'comments'
         }, // pod