Perl is not being used for large projects as much as PHP. Why? Because of a number of good reasons that many Perl advocates are ignoring:
I have belonged to the Perl community for some time and I don't know if anyone else is noticing this, but the same websites are always referenced when discussing large projects. These sites are etoys, Amazon, CNNSI, Slashdot, Wired, TicketMaster, and few others. How long and impressive do you think the list of sites using Java and PHP are?