It's not the socket that invokes your script, it's a web server or some other server process. Perhaps you can configure them to pass a command line argument. In the case of CGI, you typically have cgi environment variables set up for you that you might try to detect.
in reply to How was my script launched?
In many cases, you can replace "use" with runtime "require Foo; Foo->import(ARGS)", which you can of course predicate on the method you detected you were called with. Best.pm also has some goodies for conditional module loading that may suit your needs.