It doesn't mean anything in Perl. The comment is a demonstration of why some criticisms of Perl are unjustified, as people love to make up little things like that, then other people such as yourself end up with the impression that sort of nonsense is ordinary Perl.

(You could imagine at a stretch those characters as part of an unrealistic expression, like "print $_%@array" meaning "print the value of $_ modulo the length of @array", but you can write messy code without spaces like that in many languages.)

I used to think heavy criticism of Perl's use of punctuation characters were valid, until I looked at PHP, Ruby and Rust, and realised that some of the more popular and even loved languages are punctuation-heavy too. I prefer languages with less punctuation (despite doing expert level Perl), so I think the use of sigils ($variable) is not the best design space, but I think the criticisms of that kind which single out Perl are more like a have-a-go meme than a level-headed comparison by now.