This gets into some web server configuration specific stuff. You don't have to use .cgi for the extension. .pl is ok too. You can see this even without a server. Make a short .pl cgi script that just displays a page and you can navigate your browser to that file and it should run and display the result in browser provided that you have .pl associated with the Perl interpreter. This association only works for you as a user.

So assuming you are running IIS on Windows platform, you also need to teach the server that .pl means a perl script. Use Regedit32, go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters\ScriptMap, choose add value from tool bar. In the field labeled Value Name, type in .pl and use data type REG_SZ. When the String Editor dialog box shows up, type in C:\Perl\bin\perl.exe %s %s and hit OK. Now IIS should also understand what to do when it sees .pl. Of course adjust path name to perl.exe if you've installed it a different place.