I have to admit the last time I wrote anything larger than short scripts in perl was in the perl 4 period (on HP-UX to boot). I eagerly awaited the perl 5 version of the Camel book, but in the end I jumped ship to python before getting seriously into perl 5.
That said the Perl that you write in a one-liner should be different than the Perl that you write when the complexity rises.
If you have more than a few hundred lines, you probably need to move some of it out into a module. There should also be tests for that module. It might even make sense to structure it like a CPAN module so that you can use the existing tools to test and install it.