If you spread it out,

"foo @{[ F ]} bar"
[download]

you get

my @anon_array = F;
my $anon_ref = \@anon_array;
"foo @{ $anon_ref } bar"
[download]

As you can see,

• @BLOCK (@{ STATEMENTS }) is an array dereference, not "a hash".

• [ LIST ] is an array constructor, not "an array index". It creates an array, assigns the result of LIST, and returns a reference to that array.