I want to print the contents of @INC from the Shell,is it possible?

Yes, easily:

perl -e "print \"@INC\""
[download]

This will work on *nix & Windows. On *nix you don't need to juggle with quotes as much.

Do we always need a .pl file?

No. See the above example

If type 'perl' in the shell, the cursor moves to a new line and receives my input, but the commands I enter there are not executing.I use CONTROL+C to return back to shell.

Use Control-D on Unix variants or Control-Z on Windows

Have a look at PerlMonks FAQ and The Perl Monks Guide to the Monastery for more information on how the Monastery works. Voting/Experience System is essential reading if you intend to be here for some time. Finally, don't forget there's hundreds of thousands of posts here, Super Search is your friend.

Finally, welcome to the Monastery. I hope you enjoy your stay.

update: added pointers to FAQs