Errors and functions and modules are all part of the same programing. You can see the success of some comands and why others fail. (but you know that finally it should all end as expected, don't you?)

You need to know them all. That means, practice.

Everybody needs to be able to read a log file and understand what was happening when your code was executed. Nobody is able to stay watching their scripts while they are working all the day long. So, the errors at the log files report how did it all work while you were not present. You also need to post your errors when you make a question here. Errors, explain a lot more than what our experience might know.

Everything that the errors might mean that you don't understand can be found at the perldocs. At this state of the perl language, it is very difficult to discover something that so many developers might have missed fixing, I guess.

But, I am sure that what would amaze you, like it does to me, is how many things can be achieved with this crazy perl language! Try all what the perldocs suggest, and you will see!