The syntax
@array->[0] is unsupported; it was never really intended to work in the first place.
The perldelta that comes with 5.6.1 explains:
Arrow operator and arrays
When the left argument to the arrow operator "->" is an
array, or the "scalar" operator operating on an array, the
result of the operation must be considered erroneous. For
example:
@x->[2]
scalar(@x)->[2]
These expressions will get run-time errors in some future
release of Perl.
I think that your tutorial is somewhat misleading, because you seem to suggest that
@array->[0] is a standard idiom.