I don't know of any scripts to do this automatically, because it's generally considered pretty silly. Your code is copyrighted by yourself (unless you did it
for them, in which case they own it and the copyright, obfuscation or no), and so long as you set down the terms of the license to your customer (being careful not to infringe upon any licenses for code you've included in your application, such as GNU or the Artistic license), they are bound to do with your software what you let them do. If they do not, sue them and revoke their license.
If you're still bent on trying to obfuscate the code for whatever reason, you'll just have to go about it by hand.. Change all of your variable names to, like, $a1, $a2, $a3, etc., remove white space and indentation, and perhaps encrypt static strings (via a simple XOR algorithm) so that it's difficult to read.
Finally, if you want to get real nasty about it, encode your script (via XOR or RSA if you feel it's necessary), put it in an __END__ block, and read/decode/eval on the fly.
Before you go through all of that work, though, ask yourself why you need this obfuscated. Perl code must be distributed in source form. It's not possible to keep people from figuring out how you do it. In the US at least, copyright and contract law (license) should offer you enough protection so that you don't have to worry about silliness like this.