If your going to use $_ anyway you might as well use the more efficient modifier form (no scope handling overhead).

@foo[$_-1,-$_] = @foo[-$_,$_-1] for (1..@foo/2);
[download]

BTW: I think this is probably the best implementation (starting at one instead of zero) of all that have been present along this line (especially including my embarrasing fencepost error version) so ++ to you.

Yves / DeMerphq
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Software Engineering is Programming when you can't. -- E. W. Dijkstra (RIP)