Improve guard so it works for no eof new line

ftplugin/xs.vim

@@ -1,4 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'perl') == -1
+
 " Vim filetype plugin file
 " Language:      XS (Perl extension interface language)
 " Maintainer:    vim-perl <vim-perl@googlegroups.com>
@@ -13,4 +14,5 @@ endif
 
 " Just use the C plugin for now.
 runtime! ftplugin/c.vim ftplugin/c_*.vim ftplugin/c/*.vim
+
 endif