You have the option of "compiling" your perl code into an ActiveX control, then you'll just be providing the client with the created .dll file.

Since you mentioned an IIS server, it would be very simple to throw together small ASP pages to call your "cool" routines.

Dim Obj as Object
Set Obj = CreateObject("ProgID_of_your_Perl_DLL.app")
Obj.CoolRoutine
[download]

Update:
It was late when I first posted this so forgive me for not providing a pure Perl solution. This is PERLmonks after all and it ate at me so bad that I climbed back out of bed to add this to my post:

Once the .dll is on the server and registered properly you can call it via you Perl CGI scripts by adding:

use Win32::OLE;

my $obj = Win32::OLE->CreateObject('ProgID_of_your_Perl_DLL.app');

$obj->CoolRoutine();
[download]

-Nitrox