Actually, your imagination is defeated by the reality. You have to convince W3
to change how perl works and the owner of the site you are trying to download
from, to upgrade to your imaginary version of perl & cgi. Only then the
existing httrack will be able to meet your expectation.

Please read about perl to know if it is possible.

The only way I see now is to convince the website owner to hand over the perl
script to you.

If you think my language is a bit rude, I couldn't control myself after I saw
the subject of this message.

Let me settle this down and help you a bit: 
PERL: <http://en.wikipedia.org/wiki/Perl>
CGI: <http://en.wikipedia.org/wiki/Common_Gateway_Interface>

CGI is just an interface. As per the current standards, what you expected can
not be realized.

HTTrack can only fetch what the servers offer to everyone using regular
browsers. Webservers do not serve the pl file, it only serves generated pages,
like the ones that you've got.

Please do not hesitate to ask again if you haven't understood anything.

Regards
Annajiat