If you are using active state Perl, it installs a ISAPI module. It is a DLL, and doesn't actually run the perl.exe itself. Here is an excerpt from the active state docs. Check to see if the server is using this instead.

What is ISAPI?

ISAPI (Internet Server Application Programming Interface) is an API for writing extensions to web servers. It was originally developed by Process Software, and adopted by Microsoft as its standard server API. It complements or replaces the Common Gateway Interface (CGI), the standard interprocess protocol for writing extensions to web servers.

ISAPI's main advantage over CGI is that it uses dynamic-link library (DLL) function calls to communicate with extension components, rather than environment variables and standard I/O, as CGI does. There's a lot of overhead when starting new processes on Win32 platforms, and DLL calls eliminate the need for new processes, thus reducing the running time.

Although it was originally developed for Microsoft Internet Information Server, many Windows NT-hosted web servers now support ISAPI. See What HTTP servers support ActivePerl? for the names of a few. If your server isn't there, check its documentation.

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What is Perl for ISAPI?

Perl for ISAPI, is an ISAPI extension that runs Perl scripts on Win32 platforms.

Perl for ISAPI is mainly used for creating dynamic content on World Wide Web sites. Writing Perl scripts that run under PerlIS is not much different than writing scripts for the Common Gateway Interface (CGI).

Perl for ISAPI doesn't have much general purpose use. For general purpose programming, stick with the perl interpreter (perl.exe).

You may also see Perl for ISAPI referred to as PerlIS. PerlIS is the name of the Perl for ISAPI DLL.