The [1..4] in list context is used with slices -- it doesn't create a list context on its own. Because you ask for $a->, you're telling Perl to dereference $a to a single element, not a slice, thus 1..4 is interpreted in scalar context.

In the case that works, you're dereferencing $a to an array, and then taking a slice of that -- and because you're slicing, 1..4 gets interpreted in list context.

$a->[1..4];  # not a slice
@{$a}[1..4]; # slice
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