... complains that you "Can't localize lexical variable @array", but it has no problem localizing $hash{foo}.

It has no problem localizing the value of an array element, either:

my %hash;
my @array;

{
    local $hash{foo} = 'bar';
    local $array[1]  = 'foo';
    print "inner scope:\n";
    print "$_ => $hash{$_}\n" for keys %hash;
    print "[$_] $array[$_]\n" for 0..$#array;
}

print "outer scope:\n";
print "$_ => $hash{$_}\n" for keys %hash;
print "[$_] $array[$_]\n" for 0..$#array;
__END__
inner scope:
foo => bar
[0] 
[1] foo
outer scope:
[download]

Were you trying to localize the entire hash - as you did with @array - perl would complain also:

Can't localize lexical variable %hash at foo line x.
[download]