Sorry, perl.j, because in this and some of your other posts, I see (well, 'infer') an effort to learn "more" (for some large value of "more") about Perl, but - - for posting yet another question that could be answered by a bit of your own research (...and a whale of a lot of study).

And perhaps it didn't occur to you, but while an answer to your first question is not all that verbose, a decent answer to the second would occupy a fair-sized library.

Also important: you'd probably learn a lot more (including some gotchas, exceptions, tangential facts, etc) by doing your own research and study.

So, extending the reply above, you will profit from reading and learning from perldoc perltoc (which, with any reasonable install, should exist on your local machine).