The @{...}...appears to be an (possibly incorrectly written) dereferencing; I don't think it's relevant to the question.

Since the anonymous OP didn't say, it's not possible to know which part wasn't understood. It's quite possible the OP threw up his/her hands in bewilderment at the whole thing, without even trying to break it down into pieces.

The @{} is correct (in that it does what was presumably intended), just poorly written. It is a one-element slice in scalar context, where a simple array element would have done.