If you have access to an error_log, look at that. Otherwise, it usually means you either have the wrong permissions (wakaba.pl should be 755), or the wrong hashbang (the #!/usr/bin/perl line at the start - usually this is correct, but on some servers you have to change it. Many Windows servers want it to be just #!perl).

Also, this is a useful thing to try: http://wakaba.c3.cx/sup/kareha.pl/1102836129/6