Just call tech Support at Interland and ask them to Register .cgi extentions to perl...
Or you can place an incident report...If they tell you they are already registered, give them the error message, and tell them this error means cgi is not registered..(check it again before you call)
It will only take them a few minutes to fix this ( but they may not do it until they reset the servers(which is done every morning))You don't have to change .cgi to .pl on Interland they will fix it for you..