Why system operation cann't find the interpreter??

dspti

system operation:Fedora Core 2

perl version:

This is perl, v5.8.3 built for i386-linux-thread-multi
Copyright 1987-2003, Larry Wall

%which perl
/usr/bin/perl

In the program hello

#! /usr/bin/perl  
print "Hello!\n";

%chmod +x hello
%hello
hello: Command not found.

%perl hello
Hello.

why?????