Perl starts out as a world unto its own, full of strange symbols, it is shrouded in a world of mystery and obfusaction (or not :) ).
Admit it, part of the charm of perl is writing some obscure JAPH one-liner, being able to get 'shebang' jokes, and knowing what the heck $$->a->razzle()->dazzle might actually accomplish.
But how to get there? You've probably read the Llama and the Camel. You've probably got some bigh honkin scripts out there doing some heavy lifting. Heck, you may have cobbled a RegEx together that unravels the Necronmicon. All this and yet....
Odds are you came from a C-ish or similar background and you realize that you're still writing C or Java, but in Perl.
This book is the Emerillian kick to the next level. Realizing that languages, Perl especially, have idioms, best practices, standards, Hall acquanints you with them.
Just as children are baffled by "a fork in the road" you may find handy idioms like my ($b) = ($a=~m,(^\w+?),) something you have to look up, or memorize -- but later you'll realize that you *needed that* phrase in order to round out your vocabulary (just like a 'fork in tho road').
Hall also makes good suggestions that will help make your code tighter, helping your banish overuse of globals (impossible for someone else to maintain). He teaches you to document and follow standards.
this book was critical in my development form perl-plateaud and stymied, to perl-proficient.