updated for version 7.3.820
Problem:    Build errors and warnings when building with small features and
            Lua, Perl or Ruby.
Solution:   Add #ifdefs and UNUSED.
diff --git a/src/if_perl.xs b/src/if_perl.xs
index cdfac90..67ffe18 100644
--- a/src/if_perl.xs
+++ b/src/if_perl.xs
@@ -600,9 +600,9 @@
  */
     char_u *
 eval_to_string(arg, nextcmd, dolist)
-    char_u	*arg;
-    char_u	**nextcmd;
-    int		dolist;
+    char_u	*arg UNUSED;
+    char_u	**nextcmd UNUSED;
+    int		dolist UNUSED;
 {
     return NULL;
 }