I assume you are using apache then? with the .shtml ext
if so then it is your syntax, like so would be better
<!--#include file="poll.pl" -->
and check out this
[httpd.apache.org...]
1. Does your script prints "Content-Type: text/html\n\n" at the beggining?
2. Did you configure IIS to understans SSI directives within .shtml files?