You are correct. They are valid.

When I ran mhearse's example code I got the following error:

  Array found where operator expected at format.pl line 17, at end of 
+line
  (Missing operator before ?)
  syntax error at format.pl line 17, near "@ @ @ @ "
[download]

I misinterpreted this to mean that the bare @'s were the problem. However, as you point out, they are in fact valid and the error comes from the line wrapping around.

In which case, I can't say what is the problem. Setting $= to 600 or any other value works fine for me with perls from 5.00405 onwards.

--
John.