Do other scripts with the pl extension work correctly? If not, check the application settings under the web site in IIS manager. These can be found by right clicking on the default web site, choosing properties, then clicking configuration at the bottom of the "Home Directory" tab. You should find that .pl is listed under mappings with an executable line something like C:\Perl\bin\perl.exe "%s" %s and Verbs limited to GET,POST. If it is not there, just add it in. If it is check for execute permissions on the cgi-bin folder under IIS manager and the file system

Assumptions, that Windows/IIS Platform is being used and Perl.exe is located at c:\perl\bin\perl.exe since #!c:\perl\bin\perl