I realize that the question is about online sources, but I taught myself Perl in about three weeks thanks to the following books:
Learning Perl
Intermediate Perl
I already had a little bit of background knowledge in C, but the way these books teach is phenomenal. Scripts I've written in Perl are currently powering the data analysis process used by some instrument teams on the UA/NASA Phoenix Mars Lander - and I'm a junior in college! If it's good enough for NASA, it's good enough for you :)