One way to wrap a perl program is to use a web server. Create a server that takes an input of two strings and return the relatedness. The server can keep WordNet loaded between requests.
The server could be something like Apache and mod_perl, or it could be something like POE::Component::Server::HTTP.
I use the Cygwin environment and the POE modules to interface to other programs this way. However, I wasn't able to get POE working well until a learned a fair amount of Perl. Maybe you will get lucky and find a POE example that is very close to what you need.
This might not be the 'absolute simplest' to develop, but after you get it working your code will be quite simple!
It should work perfectly the first time! - toma