We can set password on a file using vi -x but when I am setting password on Perl script using vi -x, I am unable to execute the script as it is giving error. (because vi -x is adding some unknown characters to script) Is there any workaround to it?

Um, you're confused. Once you encrypt the script with "vi -x" you have to decrypt it before you can run the program -- thats how encryption works

Module::Crypt - Encrypt your Perl code and compile it into XS
PAR::Filter::Crypto - Encrypt Perl files in PAR archives
Module::CryptSource - Encrypt and Decrypt source for Binary Packagers
Why is it bad to hide the source?
How can I hide the source for my Perl program?
Code Encryption .. How to ??
encrypting perl code used with mod_perl
simple encryption for perl files