If your Perl skill can placed into Amateur, Intermediate and Advanced levels, how would you know where you Perl skill level is? It's probably obvious in some cases but are there indicators to help you determine whether you've progressed beyond the Amaterish level and so forth?

Reading I present to you... Horrible code!, I get the sense that that sort of code is the result of two things: first, not knowing enough Perl ways and second, not knowing enough programming techniques (e.g. refactoring).

There must be some Perl constructs or syntax that is considered more advanced. What are those? OOP is considered an Advanced Topic in Programming Perl, so does not using OOP imply an Amateurish level of Perl knowledge?

Thanks in anticipation for reading and sharing :)