Evidently, this is a feature of Perl 5.6.

Check out Camel3, page 283. The last two sentences of the section: Hashes of Functions.

". . . we invoke the appropriate command by derefencing the hash value as a function and pass that function and empty argument list. We could have dereferenced it as &{ $HoF{lc $cmd} }(), or, as of the 5.6 release of Perl, simply $HoF(lc $cmd}().

Carl-Joseph