How can a script (.cgi & .pl) be written to be used on only 1 domain name? I don't want people to buy my script and then use it on multiple domain.

Is there a way to do this? I have heard some people that say this can be done but I don't know how. Any experts in here?

With scripting where you can view and alter the source any checks you input to the script can be removed easily, there are a few methods of compiling/encrypting scripts but it usually invovles special software to be installed on the server and since most people use vhosting they can't install the software....