How does this CGI get invoked ?
It would be invoked/executed by your webserver(apache), upon receiving requests from web client programs
will perl interpreter be able to understand .cgi extension ?
yes it can
a good tutorial is here
http://perltraining.com.au/courses/webdev.html, I suggest you to read it, before doing any big time activity on CGI
Vivek
-- In accordance with the prarabdha of each, the One whose function it is to ordain makes each to act. What will not happen will never happen, whatever effort one may put forth. And what will happen will not fail to happen, however much one may seek to prevent it. This is certain. The part of wisdom therefore is to stay quiet.