The most annoying thing is having to go on the web to find a doc. PHP is horrifying enough and then you read the docs and find all the exceptions to whatever rule (and the bugs) in the comments.

For Perl:
perldoc -f [function name]

Or perldoc [Module::Name] (also man Module::Name works on most Linux distros)

Also on Linux, 'man perl' gives a list of a whole ton of man pages that give you specific information on regexes, objects, references, syntax, variables, etc.

And if you have to have it in a pretty web interface it is indeed all online
(module docs are as well)

Say what you want about Perl but it has tons of useful modules and it is very well documented.