Thanks for such information on the web.

I actually want to write a perl program which will just display the IE version of the machine on which I will execute this perl program.

What are you trying to do?  IE is a client program (a browser), but Perl usually lives on the server for running CGI scripts.   In those, you'll find an environment variable $ENV{HTTP_USER_AGENT} which contains the information you're looking for.  Here's an example of the string in the variable:
     Mozilla/4.0 (compatible; MSIE 5.22; Mac_PowerPC)

Which you could tackle with a regular expression such as
     /MSIE\s+([0-9.]+)/
to get the version number into the variable $1.

If you are truely looking for the version(s) or IE that are present on a system on which you are running a Perl program, yes, the registry will contain many settings that might be useful clues;  not something I've researched in depth, but if you use the programs that we have around and on our web site / in our courses, they will give you a framework from which you can search and experimentally find what the information you need is.

or if you're using CGI.pm $query->user_agent(); does the same trick, but using CGI which is generally recommended.

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