Amazing!

I think I would searched for this for years, but once I see your explanation, it becomes clear.

BTW, the reason why I thought it would be related to sub is that the similar code

my $f={$xnix => 100}->{'X'};
[download]

works fine, but of course now this is clear too: In the latter case, there is no ambiguity, so it is correctly parsed as a hash. Thanks a lot for helping!