You need to have a book of perl,and than you can start writing small scripts related to data extracation from a file, string handlings and then you can go for more larger scripts.
If you are working on any project, then you can make a script for tasks which you want to automize (like code generation , testcase generation , regression running.. etc.)
I assume you have the perl package installed at your system. Perl is mainly used for the text processing. So try out very basic programs like patter search a string and print it on screen, take some numbers as inputs and find out the largest/smallest. Try out basic programs, when you are okay with that, proceed with the hashes.
Type - perldoc perlintro on your command line. Its a very good way of learning perl.