use strict;
use warnings;
use Tie::IxHash;

my %myhash;
my %myotherhash;

tie %myhash, 'Tie::IxHash';
for (my $i=0; $i<7; $i++) {
    $myhash{$i} = 2*$i;
}
my @keys = keys %myhash;
print "@keys\n";

for (my $i=0; $i<7; $i++) {
    $myotherhash{$i} = 2*$i;
}
@keys = keys %myotherhash;
print "@keys\n";

__END__
Output:
0 1 2 3 4 5 6
6 4 1 3 0 2 5