I am new to any scripting language. But, still I worked on scripting a bit like tailoring other scripts to work for my purpose. For me, what is the best online resource to learn Perl?
If you are a beginner, I would suggest you take a look at the cookbook provided by PLEAC. You can find it at http://pleac.sf.net. There you can find cookbooks for most languages.
If you already know a bit of perl, PerlMonks is a great online resource. You can ask questions in their Seekers of Perl Wisdom section and the answers are often of very high quality. Many people who keep up with the latest developments in Perl hang out there.
As an added bonus, if you ask a clear question, many times the people there take the time to look at the underlying problem and will point out alternate approaches rather than simply taking your question at face value.
I highly recommend starting with Simon Cozens' Beginning Perl book.
And also, reading the Perl documentation.
Perl is in a state of (comparatively) rapid change, and has gotten into the position where the best documentation beyond a basic introduction to Perl 5 -- the current major version -- is the electronic documentation which comes with the language itself.
Read 'perldoc perlintro', then look to 'perldoc perl' for the rest of the core language documentation. Note that on Debian systems, you'll need to 'apt-get install perl-doc' to get this documentation.
Once you've got a handle on things, check out 'perldoc perldelta' to see what's new in the version of Perl installed on your system (which should be 5.8.8 or 5.10 these days -- much cool stuff in 5.10!). If the perldelta page isn't making any sense (and believe me, I remember how that feels), just come back to it later.
Finally, freenode #perl for questions you can't find answers to in the docs.
The perldoc documentation is the best source for understanding how to use the language well.
The camel book "Programming Perl" is an excellent printed reference with thorough explanations written by the same people who wrote the perldocs (other books with animals on them are mostly ok.) Beware online tutorials - many of them teach very sloppy perl.
Use 'warnings' and 'strict' - then perl will be very helpful in pointing out your errors.
Perlmonks is also great (they will also tell you to use 'warnings' and 'strict'.)
And then you have to learn the CPAN one module at a time (which is where perlmonks and mailing lists are very helpful.)
I would very much recommend Programming Perl, but beware you may need a subscription to Safari in order to read it online.
As other people noted, the online book Beginning Perl has a good reputation and is written by a very clueful expert and active Perl contributor. Other than that, I concentrated resources for beginners in the Perl Beginners' Site, and you can probably find something there that would be to your liking.
I realize that the question is about online sources, but I taught myself Perl in about three weeks thanks to the following books:
I already had a little bit of background knowledge in C, but the way these books teach is phenomenal. Scripts I've written in Perl are currently powering the data analysis process used by some instrument teams on the UA/NASA Phoenix Mars Lander - and I'm a junior in college! If it's good enough for NASA, it's good enough for you :)
The Official Perl 5 Wiki is a great resource with lots of info and links, and it aims to be beginner-friendly.
Also see the bottom of the wiki home page for the latest headlines from the Planet Perl feed aggregator. It's useful to skim over every few days, because it sometimes answers questions that you didn't know enough to ask, but which you should be asking.