Agree 100%. If I'm scanning some code, and I see $LIST_SEPARATOR, unless I've memorised everything in 'use English', I might not realise that it's from there. I might think it's a global constant defined somewhere else (and I've had to work with code that defines globals all over the place).
If I see a punctuation variable, I know immediately that it's a special Perl variable. For better or worse (and often worse) Perl has many of these, and I could only name a handful, because I barely use them myself. But that doesn't mean others don't use them, and I might have to maintain (or just read) their code. I'd much rather they used the punctuation versions - it helps reading for me immensely.
Kind of ironic in a way, because this is just the sort of thing that people outside of Perl claim makes Perl code so unreadable.