Right, in list context an arrays and hashes are flattened into a single list e.g

my @a = qw( foo bar baz );
my %h = qw( one ichi two ni );

## print evaluates it's args in list context
print "array: ", @a,$/;
print "hash:  ", %h,$/;
print "a & h: ", @a, %h, $/;

__output__

array: foobarbaz
hash:  oneichitwoni
a & h: foobarbazoneichitwoni
[download]

Now with nested data structures this is still exactly the same as references aren't automagically dereferenced e.g

my @a = ( ["one"], ["two"] );
my %h = ( a => \@a );

print "array: ", @a, $/;
print "hash:  ", %h, $/;

__output__

array: ARRAY(0x80fbb0c)ARRAY(0x80fba1c)
hash:  aARRAY(0x8107d84)
[download]

So because subroutines' arguments are evaluated in list context an AoA is fine and dandy to pass about without having to create a reference to it.
HTH

_________
broquaint