I don't think that is why with Perl. Granted it's been over a decade so opinion might have changed but when I was in college Perl had a reputation as being a "write only" language. Where unless you had comments / documentation to explain it to you, if you encounter code you didn't write (or you wrote 6 months ago) good luck figuring out what it does.
All languages are like that to a certain extent but Perl more than others.
I had a lot of junior folks complaining about "un"readability of my Perl codes back when I used to work in finance. There were a lot of seasoned Java and C++ programmer on the business side who didn't have much problem hacking their way around Perl, but most folks on the operational side had less than a few year of shell, Python, PHP. I ended up rewriting their codes for speed, brevity and correctness -- and it drove them crazy.
But I've also seen a fair share of properly functioning, yet incomprehensible Perl codes so I could see why so many are turned off.
Perl definitely can be "write only", but it doesn't have to be as long as you don't try to be too clever, but I could say the same about most languages. I wouldn't want to work on a stack that was centered around Perl, but it is fantastic for quick one off scripts or relatively simple file processing tasks
All languages are like that to a certain extent but Perl more than others.
Edit: fixed "read only" to "write only"