my %hash;
@hash{ 3,4 } = qw( perl hacker );
print join ",", keys %hash;      # prints "3,4"
[download]

my %hash;
$hash{ 3,4 } = qw( perl hacker );
print join ",", keys %hash;      # ????
[download]

I initially thought that the comma operator, forcing output as a list, would be done first, and thus the hash step would convert the list to a scalar (or in this case, '2') and use that as the key, but I was wrong. When I ran this, I got "34", that is, there was a single key in the hash. But this was on linux; on windows (both 5.005 and 5.6.1), I got "34" (if that doesn't come out correctly, the middle symbol looks like a reduced capital L.) A bit more digging shows up that linux actually has an invisible symbol there, represented by less as '^\'. Weirrrd.

Thinking that the hash might be interpreting this strangely, I tried the following:

my %hash;
$hash{ (3,4) } = qw( perl hacker );
print join ",", keys %hash;      # ????
[download]

Again, the same result occured.

Obviously, going to :

my %hash;
$hash{ [3,4] } = qw( perl hacker );
print join ",", keys %hash;      # ????
[download]

gives "ARRAY(0xDEADBEEF)" or some such like that, which isn't a surprise at all.

Was this reliable?

my %hash;
$hash{ 3,4 } = qw( perl hacker );
print $hash{ 3,4 }, "\n";
[download]

Which results in "hacker". Very interesting...

Variables work with no problem:

my %hash;
for my $i (0..5) {
  for my $j (0..5) {
    $hash{ $i,$j } = $i*$j;
  }
}
foreach ( keys %hash ) { print "$_ : ", $hash{ $_ }, "\n"; }
[download]

This code prints out the correct multiplication with each 'key'. This also works with any number of 'keys', eg expanding the above to $i, $j, $k.

So I have tumbled accidently into a way to do multidimensional hashes? I know this isn't the most elegant solution, but something seems to be working. Would it be possible to split on this odd key, such that one can make grep { nth_element_of_the_key eq 'test' } keys %hash;

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain