--- a/upload.pl	Fri Nov 20 17:57:22 2015 +0100
+++ b/upload.pl	Mon Feb 01 11:36:32 2016 +0100
@@ -108,7 +108,8 @@
       or mkdir $DIR => 0750
       or die "Can't mkdir $DIR: $!\n";
 
-    if (param("delete") =~ /([-a-z\d]+-\d+-.)/i) {
+    my $delete = param("delete");
+    if (defined $delete and $delete =~ /([-a-z\d]+-\d+-.)/i) {
         deletedir $1;
         print redirect(-uri => url(-path_info => 1));
         exit 0;