It's not that I think reading it is necessarily bad, but Perl does shift the onus of writing from making it correct to making it legivlem later. It's easy to write correct perl code, there's often many ways to do it because the language tries to do what you want for you. That unfortunately makes it harder to read, as when not in the exact same frame of mind, those shortcuts the language does for you are harder to intuit later.

I think the total amount of effort required to write good legible code is about on par with it's contemporary languages if you take the time to write it well, but it's hard to resist being able to write it quickly and be done because it's easy to ignore the problem of tomorrow you're creating by being so quick and productive today.