With a stream cipher like RC4, it's extremely important that you NEVER ENCRYPT TWO MESSAGES WITH THE SAME KEY. If you do, the security reduces to that of simple xor encryption -- in other words, no security at all. This problem is mentioned in the Crypt::RC4 docs. Using a string hardcoded into your script as the key is the wrong way to use this module.

If you want an out-of-the-box encryption solution, I would recommend Crypt::CBC. There are pure-perl encryption modules you can use with it, if compiling modules is a problem for you.