Something that has not been mentioned yet, but that just at the same time is obvious is gradual learning by means of exchange of ideas with more experienced users, mostly during the course of trying to accomplish a well definite practical task.

I, for one, made my very few first steps in perl with the aid of a borrowed Perl4-based (I guess) "Learning Perl". Then I began asking for advice on clpmisc and for sure I've learnt more about perl there than anywhere else.

Of course everything is in the docs, but for obvious reasons it's far too easy to overlook potentially precious pieces of information, maybe because we just think that they're not fundamental for us at a certain point...

For example stuff I've been surprised to discover at first and that has been "revealed" to me in the course of discussions includes (but is not limited to!):

• the possibility of putting coderefs (or more generally perl code) in @INC,
• the possibility of open()ing strings as files in memory,
• the possibility of open()ing temporary anonymous files,
• smart symbol table manipulations.