To amplify a bit on what JavaFan said above: no matter how you happen to get started, you really really should make it a point to become familiar with the man page and use it regularly -- particularly the one that comes with the particular version of perl that you happen to be using. That is, get into the habit of using the command line perldoc perlre. The output is long, but the payoff is great.

The reason is that the man page is intended to be the official reference. Care is taken in each perl release to confirm that the man page in that release fully reflects the current state of the regex engine in that release.

And you don't have to worry about carrying books around with you, or having web access, in order to look stuff up. If you are using perl at a given moment, you have access to the regex man page at that moment. So learn to use it, no matter what other resources you might want to use.