PS If anyone can tell me how to get this hash-flattened-into-an-array behaviour without a sub, I'd be interested. I've been fiddling around with the syntax trying to get that.

if ( "@{[%hash1]}" eq "@{[$hash2]}" ) {
    # foo ...
}
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None of these repsonses sort the array. I would have thought that this solution would be flakey unsorted since hashs can come out in any order they please...

I do flattening for comparison by shoving a hashref into an array ( @foo = %{$foo} ) and then sorting the array ( @foo = sort @foo ) and flattening that into a string.,p> The obvious problem with this is that if you have a hash where the keys/values were transposed then it would still appear equal. Similar situations will occur with other data anomolies.

Not a problem in my case, but worth remembering.

I was going to say that they always come out in the same order because the hashing key does not change. Unfortunately that did not stand up to testing. The order the elements are inserted into the hash makes a difference:

my ( %hash1, %hash2 );
$hash1{"value$_"} = $_ for ( 1 .. 11 );
$hash2{"value$_"} = $_ for ( 5 .. 11 );
$hash2{"value$_"} = $_ for ( 1 .. 4 );

sub flatten { return "@_" }

if ( flatten(%hash1) eq flatten(%hash2) ) {
        print "equal\n". flatten( %hash1 ) . "\n" . flatten(%hash2)
} else {
        print "not\n" . flatten( %hash1 ) . "\n" . flatten(%hash2);
}


not
value10 10 value11 11 value1 1 value2 2 value3 3 value4 4 value5 5 val
+ue6 6 value7 7 value8 8 value9 9
value10 10 value1 1 value11 11 value2 2 value3 3 value4 4 value5 5 val
+ue6 6 value7 7 value8 8 value9 9
========== [C:\users\jake\code\komodo\test3.pl] run finished. ========
+==
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sub flatten {
  my %hash = @_; 
  return join '', map "$hash{$_}$_", sort keys %hash;
}
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The answer to your question on how not to use a sub would be to use the join, map in the if clause. This saves passing the hash by value, but duplicates the logic on either side of the eq

-- iakobski