I always thought so, too.  Interestingly, according to Devel::Size, the memory usage isn't all that different: 

use Devel::Size qw(total_size);

my @a;  push @a, [$_,$_] for 1..2**16;
print total_size(\@a);                   # one array of pairs

my @b;  push @b, $_ for 1..2**16;
print total_size(\@b) * 2;               # two arrays

__END__
4964080
4740496

[download]

(tested with perl, v5.10.1 (*) built for x86_64-linux-thread-multi, Devel::Size-0.72)

PS: although there is nothing random in the data, the sizes reported by Devel::Size vary by up to 15% from call to call (i.e. on some occasions the one array with pairs uses even less memory than two separate arrays). Why is that?

In reply to Re^3: sorting two arrays together by Anonyrnous Monk
in thread sorting two arrays together by siskos1

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