My organization maintains a couple of Perl web apps for internal purposes (one that dates back starting in 1997). We do some occasional work/improvements/modernizations on these. Mentally switching into "perl" mode to work on these projects requires tons more effort then switching between our other Bash/PHP/Puppet/Python codebases. And there are several sections of the code I've shied away from modernizing because they use esoteric perl operators that I don't use and don't really understand.
Not to mention that only a few members of our organization are really "fluent" in perl, and teaching it to the newbies feels almost like a waste of resources when they can be more productive faster using python which has ample modern documentation and simpler syntax/conventions and well defined coding standards.