Interesting question and congrats for having made this discovery, some books do not even mention anything about this... In addition to the links provided to you and the previous discussions presented here, I can enumerate the interesting:

1. perlintro
2. perlcheat
3. perldsc
4. perlboot

The best thing about documentations in Perl is that someone took it upon themselves to write them, others took it upon themselves to simplify them, while others took it upon themselves to make specialized examples and this is all done for our own good and we'd have to take it upon ourselves to read them -habitually- or be content when told to RTFM in some cases in order to have a full round circle of participation...

An assortment of these documents is found at perldoc.perl.org in a well classified organization and a neatly served presentation, check the Reference box to the left.