I don't trust Devel::Size, I prefer measuring externally: 
my @a;
my @b;

for (0 .. 2 ** 16 - 1) {
    if ($ARGV[0]) { 
        $a[$_][0] = $_;
        $a[$_][1] = $_;
    }
    else {
        @a[$_] = $_;
        @b[$_] = $_;
    }
}

system "grep ^VmSize /proc/$$/status";

__END__

[download]
Without an argument, I get VmSize: 11460 kB, with an argument I get VmSize: 16636 kB. Repeated runs vary by less than 10 kB. That's a difference of 45%.

However, I do notice a difference using total_size as well. Adding a say total_size(\@a) + total_size(\@b); at the end, I get: 

VmSize:       11844 kB
3670208

[download]
and 
VmSize:       16996 kB
10748112

[download]
Almost 3 times the amount of memory with array pairs than without, according to Devel::Size;

In reply to Re^4: sorting two arrays together by JavaFan
in thread sorting two arrays together by siskos1

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