The context being a deliberate effort to make it compact. You can abuse features in most languages and make it hard to read.

Who cares about "compactness"? You weren't golfing. It just sticks out as bad code.

Not my code, it was copied (note the attribution) from a specific context where somebody cared about compactness.

Edit: Perl's also not the only language that supports the comma operator, predicate if, ternary, and other things that seem to bother you.